The Book of the Sea the Realms of the Baltic Sea

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The Book of the Sea The realms of the Baltic Sea

BALTIC ENVIRONMENTAL FORUM 1 The realms of the Baltic Sea 4 THE BOOK OF THE SEA 5 The realms of the Baltic Sea The Book of the Sea. The realms of the Baltic Sea

2 THE BOOK OF THE SEA 3 The realms of the Baltic Sea The Book of the Sea The realms of the Baltic Sea Gulf of Bothnia

Åland Islands Helsinki Oslo Gulf of Finland A compilation by Žymantas Morkvėnas and Darius Daunys Stockholm Tallinn Hiiumaa

Skagerrak Saaremaa Gulf of Riga

Gotland

Kattegat Öland Riga

Copenhagen Baltic Sea Klaipėda

Bornholm Bay of Gdańsk Rügen Baltic Environmental Forum 2015

2 THE BOOK OF THE SEA 3 The realms of the Baltic Sea Table of Contents

Published in the framework of the Project partners: Authors of compilation Žymantas Morkvėnas and Darius Daunys 7 Preface 54 Brown shrimp project „Inventory of marine species Marine Science and Technology 54 Relict amphipod Texts provided by Darius Daunys, Žymantas Morkvėnas, Mindaugas Dagys, 9 Ecosystem of the Baltic Sea and habitats for development of Centre (MarsTec) at Klaipėda 55 Relict isopod crustacean Linas Ložys, Jūratė Lesutienė, Albertas Bitinas, Martynas Bučas, 11 Geological development Natura 2000 network in the offshore University, 57 Small sandeel Loreta Kelpšaitė-Rimkienė, Dalia Čebatariūnaitė, Nerijus Žitkevičius, of the Baltic Sea waters of Lithuania (DENOFLIT)“ Institute of Ecology of the Nature 58 Turbot Greta Gyraitė, Arūnas Grušas, Erlandas Paplauskis, Radvilė Jankevičienė, 14 The coasts of the Baltic Sea (LIFE09 NAT/LT/000234), Research Centre, 59 European flounder Rita Norvaišaitė 18 Water balance financed by the European Union The Fisheries Service under the 60 Velvet scoter 21 Salinity LIFE+ programme, the Republic Ministry of Agriculture of the Illustrations by Saulius Karalius 60 Common scoter 24 Food chain of Lithuania and project partners. Republic of Lithuania, Photographs by Žymantas Morkvėnas and Erlandas Paplauskis 63 Reefs 26 Ice cover Project implementation period: State Service for Protected Areas Maps compilation by Ingrida Bagdanavičiūtė 71 Black carrageen 28 Water currents 2010–2015. under the Ministry of Environment, Design by Gedas Čiuželis 71 Green branched weed Baltic Environmental Forum Lithuania, Edited by Rita Maksimavičienė The realms of the Baltic Sea 72 Bay barnacle Lithuanian Sea Museum 33 The swash zone 73 Mussels 39 Bladder wrack 75 Rockpool prawn 39 Sand hopper 75 Baltic isopod The authors assume sole responsibility for the content. 40 Gulls 76 European eel The content of this publication does not necessarily reflect 40 Common gull 77 Atlantic cod the opinion of the European Commission. 42 European herring gull 78 Three-spined stickleback 42 Great black-backed gull 79 Shorthorn sculpin © Darius Daunys, 2015 44 Terns 80 Lumpfish © Žymantas Morkvėnas, 2015 45 Sublittoral sandy slopes 80 Eelpout © Saulius Karalius, 2015 51 Baltic macoma 82 Freshwater fish © Translation into English. Mantas Zurba, 2015 51 Sand gaper 84 Round goby ISBN 978-609-8041-16-3 53 Lagoon cockle 85 Steller’s eider

4 THE BOOK OF THE SEA 5 Table of Contents 86 Long-tailed duck 112 Ringed seal 87 The water column 114 Harbour porpoise Preface 93 Phytoplankton 115 Deep water depressions 95 Zooplankton and dead zones 95 Opossum shrimp 121 Filamentous chemotrophic bacteria 96 Twaite shad 121 Scoloplos armiger 97 Baltic herring 122 Pontoporeia femorata 98 European sprat 122 Diastylis rathkei 100 European whitefish 124 Ostracods, or seed shrimps The word ‘Baltic’ holds many associations of great importance to us ranging from our child- 101 Vimba bream hood memories about splashing in the spatter of the sea and building sand castles, to the Bal- Nature conservation 102 European smelt tic Way–the symbol of our freedom and unity. This is a part of our history and an invaluable 127 Why is it necessary to 103 Atlantic salmon treasure. However, contrary to the citizens of many other maritime countries, a few of us are protect nature? 104 Goosander used to fully enjoy the presents of the Baltic Sea, and our acquaintance with it is often limited 131 The principles and tools of 104 Red-throated loon to summer holidays at the beach. nature conservation and Arctic loon We have very few possibilities and occasions to see the unusual sea life that takes place 134 Protected marine areas 106 Great crested grebe at some depths. Only a handful have been lucky enough. They say that personal encounters in Lithuania 107 Auks with nature and the experiences they bring make people realise the great importance of 109 Grey seal 141 References nature and the necessity to preserve it. So how can we get to know the different realms of the 111 Harbour seal 145 Index Baltic Sea hidden beneath the waves, often far away from the shore? Why should we care and try to preserve some mollusc colonies perching on deeply submerged boulders if we are likely to never see or touch them? This book is an opportunity to learn more about the Baltic Sea, its extraordinary and unique life. To see it with the eyes of the authors of different chapters, many of whom have spent countless hours at the sea bottom, on research vessels, observing sea birds or exploring variety of fish. The authors tried to introduce the marine inhabitants in such a way that they become familiar to the reader and provoke curiosity. The book is not an academic work or a textbook. The data and stories given here are just some interesting facts about our sea and its dwellers. Of course, this is only a glimpse of the secrets guarded by the sea sustaining more than 6 000 species, whose life stories have been covered by thousands of scientific articles. Acquaintance with the Baltic Sea starts in this book with the introduction to the ecosystem of the Baltic Sea and its most important and interesting characteristics. Then the reader is invited to take a closer look at several marine habitats, which we poetically compared to

6 THE BOOK OF THE SEA 7 Preface different “realms”, and their prevailing dwellers. Each described species or group of organisms are presented also in unique illustrations by Saulius Karalius, who is both an artist and a biologist. We hope that his meticulous approach will adequately reflect the artist’s respect towards these creatures of the sea and his insatiable curiosity to discover their stories. The last section of the book is dedicated to nature conservation and offers an overview of our protected marine areas. It is not very important, which section of the book you will choose to start the acquaintance with the Baltic Sea, and how much you will be able to read at a time. By spending just a few minutes, you will be able to learn about one of almost sixty species or larger groups of marine organisms, while by spending more time you might be able to explore one of the Ecosystem of the five presented submarine realms or discover some unique characteristics of the Baltic Sea. This book is dedicated to both youngsters and adults, to those relaxing on the Baltic beaches or those shopping at the fish market. To people engaged in natural sciences and to those Baltic Sea exploring charts in search for travel destinations and adventure. It is equally good for a quiet evening with a book or some lazy time at the sea coast.

Žymantas Morkvėnas, Darius Daunys

8 THE BOOK OF THE SEA 9 Preface Geological development of the Baltic Sea

In comparison with geological development of the oceans and some other seas, spanning hundreds and tens of million years, the Baltic Sea is very young, practically in its “babyhood”. Its origins date back some 400 thousand years, in the so-called Holstein interglacial stage, while the seabed similar to the present one has formed even later, in the Eemian interglacial, some 132-120 thousand years ago. The key factors which determined the formation of the Baltic Sea depression are thought to have been tectonic movements of the Earth’s crust and erosive impact of the Scandinavian continental glaciers, that have covered this region several

Baltic Ice Lake with its northern part The Yoldia Sea (11.6–10.7 thousand years ago) bordering the melting glacier Its typical species, the bivalve mollusc Yoldia arctica (13.0–11.6 thousand years ago)

10 THE BOOK OF THE SEA 11 Geological development of the Baltic Sea times. The modern Baltic Sea has also undergone a complex geological evolution since its before present. The name of the sea originates from the Latin name of mollusc Yoldia arctica, occurrence after the last glaciation till present, alternating its state between an isolated fresh which once inhabited the cold and saline basin. water body and a brackish sea with a connection to the World Ocean. This succession was de- With the intensive crust rebound in Scandinavia, the link between the World Ocean and termined by the melting dynamics of the last Scandinavian continental glacier and associated the Yoldia Sea had disappeared, and the latter was replaced by Ancylus Lake, which lasted post-glacial rebound of the Earth’s crust, global climate warming and massive melting of the between 10.7 and 8.3 thousand years before present. The water temperatures of the lake were ice sheet, followed by the rise of the global sea levels, as well as by crust fluctuations within the relatively low, as the lake was partly fed by the melting remnants of Scandinavian glacier. Baltic region and certain other processes. The name of this water body originates from the freshwater mollusc Ancylus fluviatilis, dis- The modern Baltic Sea began to emerge only after a significant part of the ice sheet, covered in the sediments of that period. produced by the latest Scandinavian continental glaciation, had melted. The first stage in the The Litorina Sea emerged some 8.3 thousand years ago, as a new connection with the formation of the Baltic Sea was Baltic Ice Lake, which covered the southern part of the Baltic North Sea opened up in the area of current Danish Straits, and saline water from the World Sea depression between 13.0-12.6 and 11.6 thousand years before present, feeding mainly from Ocean flushed into Ancylus Lake. This process was caused by the sinking of the Earth’s crust the melting glacier covering the northern part of the depression. in the southern part of the modern Baltic Sea, as well as by intensive rise of the global water The next stage was the Yoldia Sea, which occurred with the spillover of Baltic Ice Lake and level. The Litorina Sea stage was characterised by higher salinity than nowadays, which formation of the connection with the World Ocean in the territory of current Central Sweden. made it a suitable habitat for the mollusc Littorina littoraea, that later gave its name to the This marine basin lasted almost a millennium, approximately from 11.6 to 10.7 thousand years sea. It was at this stage, that the Curonian Spit was formed and amber was washed from the Sambia Peninsula into the sediments of the Lithuanian Baltic coast and the Curonian Lagoon. Nowadays, its pieces are occasionally cast ashore by waves and sea currents. Approximate- ly 3.7 thousand years ago, as the intensity of geological processes had subsided, a relatively steady water level and the present coastlines stabilised. This period is called the Post-Litorina Sea. The development of the modern Baltic Sea covers the last 700 years.

Ancylus Lake (10.7–8.3 thousand years ago) The Litorina Sea (8.3–3.7 thousand years ago)

Its name originates from the freshwater mollusc The marine gastropod mollusc Littorina littorea was

Ancylus fluviatilis which inhabited the lake widespread during this stage

12 THE BOOK OF THE SEA 13 Geological development of the Baltic Sea Prevailing coast types in the Lithuanian coastline The coasts of the Baltic Sea of the Baltic Sea

A. Increasing (accumulation) and stable coast Ancient sea coast and terrace Protective dune crest

Dune slack Berm crest

The Baltic Sea is characterised by a relatively high coastal diversity. In the northern and western Beach face parts of the Baltic Sea, bordering Scandinavia and the Jutland peninsula, where hard crystalline or Longshore sandbank sedimentary rocks resistant to wave erosion prevail near the land surface, the existing landscape Longshore trough has been shaped by erosive impact of the continental glacier and, to some extent, by accumula- tive processes at the end of glaciation. The coasts on that side were formed as the sea flooded the contour of post-glacial landscape. Tectonic processes are also important to their development: the post-glacial rebound of the Earth’s crust is most obvious in the northernmost part of the Baltic Sea, Dunes the Gulf of Bothnia, where it reaches 9-10 mm per annum. All these factors determine, that the B. Abrasion coast subject to wave erosion northern and western coastline of the Baltic Sea is predominated by the fjordic coasts, with eleva- tions ranging from several to tens of metres, which produce multiple inlets, bays and quite often Cliff even fjords or sounds, projecting up to a dozen or so kilometres into the land. The south-eastern Swedish and southern Finnish coastline of the Baltic Sea is characterised by the skerry coasts, consisting of a multitude of larger or smaller islets and rocky reefs.

Skerries are widespread along the Swedish and Finnish coasts producing an aggregation of Sandbank islets called the Archipelago. The latter covers the area of 11 000 km2 and consists of more

than 24 000 islands and islets, being one of the most numerous in the world. Morainic plain levelled out by waves and currents Completely different types of coast prevail at the southern and eastern Baltic coastline. In that part of the basin, the coasts mainly consist of sediments and deposits of diverse origin: fluvial, organic, aeolian, etc. The prevailing soils are morainic clay and sandy loams, cobble and gravel, sand, silt, clay, and, in certain locations, peat, sapropel deposits, etc. These are soft Sand Moraine Boulders and cobble or even crumbly formations, therefore those parts of the Baltic coastline are shaped by waves and currents. Fluvial deposits also play an important role in coastal formation processes in the southern part of the Baltic Sea, as well as on the eastern side of the Gulf of Finland and in the Gulf of Riga, resulting in flat coastal-alluvial plain coasts with extensive beaches.

14 THE BOOK OF THE SEA 15 The coasts of the Baltic Sea The Yoldia Sea coasts nowadays are hidden by the Baltic waters–they are a few tens of metres below the present sea level. The former existence of dry land in the place of current sea bottom and the ancient coastline are indicated by rather steep terraces in the bottom relief, as well as by casual remnants of trees (stumps or trunks), dating back some 11-10 thousand years. The Ancylus Lake shoreline is also submerged in the Baltic Sea waters, just like that of its predecessor, the Yoldia Sea. Its position is vaguely determined and remains the object of scientific discussions. Future geological studies of the Baltic seabed should help to reveal the Estonian coast of the Gulf true position of the Ancylus Lake boundaries. of Finland The most conspicuous of the ancient coastlines in Lithuania is that of the Litorina Sea. In some areas it is represented by a flat coastal ridge situated some 7-8 m above the present sea level, for instance at Būtingė, in some other locations, like Nemirseta or Olando Kepurė (Duchman’s Hat) cliff, it turns into a steep slope over 10 m high. The subsequent Post-Lito- rina Sea in most cases remained within the earlier boundaries, however, in some segments of our coastline–north of Palanga or in the proximity of Birutės Hill–one can find the relics of the previous basin immediately behind the current ridge of the coastal dunes: segments of In the southern part of the Baltic Sea, sand is carried along the shoreline by sea currents a slope hardly reaching 2 m. and waves, thus producing sand spits and shallow lagoons separated by them from the sea, In the modern Baltic coastline of Lithuania, an obvious difference exists between the Cu- so-called boddens (the Bay of Greifswald, Szczecin Lagoon, etc.). In the south-eastern part ronian Spit and the continental coast. The Curonian Spit coast is flat and sandy, and a man- of the Baltic Sea, several relatively massive sand spits usually featuring well-developed dune made protective coastal ridge shaped in the 19th century runs along its full length. According landscapes separate from the sea larger, mostly freshwater lagoons. to its dynamic status, this coastal segment can be classified a stable coast (Fig. A). On the The south-eastern Baltic area, including the Lithuanian coastline, is characterised by continental part, flat beaches framed by coastal dunes and segments of the terraces from abrasion coasts (subject to wave erosion), accumulation coasts (increasing over time) or ancient basins interchange with steep cliff segments. abrasion-accumulation coasts with frequently alternating eroded and expanding coastal The coasts are in different dynamic states. Most of them are stable coasts, which means segments. that the sediments washed away by storms are restored during calm periods. Significant areas In the recent geological past, the Lithuanian part of the Baltic coastline has often changed of the coastline, especially on the continental part, are subject to wave erosion (Fig. B), for its position and configuration. The remaining shoreline segments of the previous historical instance at Olando Kepurė cliff, or at somewhat lower cliff near Šaipiai. The least widespread basins contribute to our understanding of geological development of the Baltic Sea in the type in Lithuania are the coasts with predominant accumulation of sediments, or the so- post-glacial period, i.e. approximately in the last 13 millennia. The oldest Baltic Ice Lake called accretional coasts. shoreline is most distinctive at the Lithuanian seaside area to the north of the city of Klaipėda, where its segments are situated at 6-7 m. altitudes above the current sea level, whereas near Būtingė they are located higher–at 15-16 m.

16 THE BOOK OF THE SEA 17 The coasts of the Baltic Sea Water balance

The Baltic Sea contains some 20 800 km3 of water. If all of it were fresh, it would provide drink- Boundaries of the ing water for the present global human population for about 4000 years. A water balance equa- Baltic Sea basin tion, describing water input and loss, could be derived for the Baltic Sea, just like for any other water body. Freshwater input is provided by the rivers, collecting it from extensive areas called river basins. Together, they comprise the Baltic Sea basin covering the area of 1 633 290 km2, which is four times the size of the sea surface alone. Some 250 rivers provide the annual inflow of 440 km2 of fresh water, which would cover the Baltic Sea surface with a layer 1.17 mm thick. The groundwater inflow accounts for at most 0.5 % of the total water mass of the Baltic Sea, therefore this inflow is usually counted as part of the input provided by rivers. The major input is provided by the River Neva, followed by somewhat smaller contributions by the Vistula, the Daugava, and the Nemunas. The highest input from the rivers is in spring, when snow is melting. The Baltic Sea basin holds the human population of some 85 million, therefore water from the drainage area also brings to the sea a surplus of nutrients causing the process of eutrophication, as well as various contaminants that water treatment facilities fail to remove. Another source of water input to the Baltic Sea is precipitation, which accounts for almost 20 % (225 km3) of the total input in the water balance. Of course, precipitation is highly dependent on the changing climatic conditions, but, on the average, the Baltic Sea annually receives some 500–600 mm of precipitation. The maximal input from precipitation is in Ju- ly-August, the minimal–in February-March. Precipitation adds to the Baltic Sea not only fresh water but also various elements and substances, such as dissolved nitrogen. But, contrary to the river input, these substances and elements are brought from areas beyond the boundaries of the Baltic Sea basin. The Baltic Sea also has a connection with the North Sea via the Danish Straits which have limited flow capacity. They allow the annual inflow of some 1 180 km3 of saline sea

18 THE BOOK OF THE SEA 19 Water balance water, which is almost three times more than the input provided by the rivers. The highest input from the North Sea is in November-January, while the lowest–in May. The inflow of Salinity saline water depends on the pressure gradient and on the winds that push water from the North Sea into the Baltic. This inflow brings along marine organisms characteristic to more salty waters. The negative part of the water balance consists of the loss through evaporation and the outflow from the basin. The annual evaporation from the Baltic Sea is very close to the input by precipitation. The estimated annual evaporation is some 450–500 mm, or about 175 km3 of water. The least intensive loss by evaporation is in spring, when the sea surface tempera- Sea water contains all the elements known on Earth, most of them as the ions of different ture is still relatively low and the winds are not so strong. The highest evaporation rate is in salts (NaCl, MgCl2, K2SO4, CaCO3, etc.). The concentration of dissolved salts is defined as late autumn. Due to higher surface temperatures and a shorter cold season (when the sea is water salinity. The major input of salts is provided by rivers, but winds and precipitation also covered with ice), the southern part of the Baltic Sea looses more water by evaporation than contribute to some extent. Large amounts of salts get into sea water from hydrothermal vents the northern one. Because of lower density, the brackish water of the Baltic Sea flows into the Change of the diversity and submarine volcanoes, as well as from dissolving seabed and coastal rocks. North Sea along the surface layers of the Danish Straits. This way, the Baltic Sea looses about of freshwater, brackish water The low salinity of the Baltic Sea is determined by the two main factors: its geographic 1 660 km3 of water annually. Although the intensity of water exchange between the North Sea and saltwater species along position, resulting in limited water exchange with the Atlantic Ocean, and the substantial and the Baltic Sea varies greatly by month, by season, and by year, a complete water replace- the water salinity gradient fresh water input by rivers. Compared to the average ocean salinity, the Baltic water salinity ment in the Baltic Sea takes on the average about 25 years. In the neighbouring North Sea, for (Remane diagram) in its central part is full five times lower, so the Baltic Sea is considered a brackish water basin. comparison, complete water turnover is reached in approximately 2 years. Brackish water is defined as salty water, whose salinity exceeds Baltic Sea that of fresh water but is much lower than that of the ocean. The major input of salts into the Baltic Sea is provided by the saline water flow from the North Sea via the set of straits: Skagerrak, Kattegat, the Great Belt, the Little Belt and Øresund (Öresund). These straits have the highest water

No of species salinity in the Baltic area. If at Kattegat water salinity reaches approximately 30 ‰ (about 30 g/l), in the Gulf of Finland and Bothnian Bay salt concentrations are merely 2.5–4 ‰, and in some north-eastern straits or bays the water may be 0 10 20 30 40 50 completely fresh. At the Lithuanian coastline, water salinity Salinity (‰) usually reaches 7–8 ‰. This is the salinity one would obtain Freshwater organisms by dissolving about a teaspoonful of salt in 1 l of water. Brackish water organisms Because of the inflow of fresh water and water exchange Seawater (saltwater) organisms with the Atlantic Ocean, the Baltic Sea has rather distinctive

20 THE BOOK OF THE SEA 21 Salinity Distribution range of key stratification. Stratification of the water column is determined by the density gradients Baltic Sea species between more and less saline water layers. Diluted waters of lower density stay at the surface, while heavier saline waters sink deeper. These water masses are separated by a special stratum Baltic macoma of steep salinity shift (halocline), characterised by a sharp increase in salinity across the Cod layer. The halocline is usually situated at the depths of 40-80 m. In Lithuanian waters it is Bladder wrack at 60-80 m, the salinity changing from 7–8 ‰ above to 10–12 ‰ below it. The steep salini-

Mussel ty gradient strongly restricts mixing between the surface and deep water strata preventing transportation of the oxygen-saturated surface waters into the depths. Salinity characteristics of the Baltic Sea cause a very specific biological diversity. Al- 5 though the number of species is relatively low, the Baltic Sea holds a unique combination of organisms typical to both saltwater and freshwater habitats. With increase of salinity, the

Common jellyfish diversity of freshwater species declines, while that of saltwater species tends to grow. The biodiversity gradients of both groups of organisms are illustrated by the Remane diagram European flounder produced by German marine biologist Adolf Remane in 1934. This diagram suggests that 3 the lowest diversity of marine organisms falls in the salinity interval of 5–8 ‰ (typical to the 4 5 central Baltic Sea, including Lithuanian waters). The Baltic Sea salinity, gradually decreasing from Skagerrak all the way northwards, determines distribution of some typical marine species. For example, starfishes and sea urchins 6 do not inhabit central and eastern parts of the Baltic Sea. Water salinity affects not only physical characteristics of water and the distribution of 30 aquatic organisms, but also their reproduction, growth rates, etc. Thus spawning of cod is Common limpet successful under salinity of at least 10 ‰, and with the salinity gradient between 18 ‰ (Bay of

20 Kiel) and 8 ‰ (Lithuanian coast), the maximum size attained by Mytilus mussels decreases from 8-9 to 3.5 cm. Salinity is extremely important to aquatic organisms, because it regulates 7 10 the osmotic pressure of their bodily fluids, and thus determines the direction and speed of diffusion of various salts and dissolved gases. The balance of elements and substances neces- Common periwinkle sary for normal life functions depends on these processes, therefore some species absorb salts Green sea urchin Common starfish from the environment, some prevent them from entering their organisms, while the third group maintains the same salinity levels as the surrounding water. Marine species cannot ex- 8 Common shore crab ist under low salinity, and to many of them the Baltic Sea water is too diluted, while to many freshwater species it is already too salty. Source: HELCOM, 2010 HELCOM, Source:

22 THE BOOK OF THE SEA 23 Salinity Large (apex) predators Food chain 0,01 % Seal, harbour porpoise

Predators 0,1 % Cod

Secondary consumers 1 % Plankton-feeding fish A marine ecological food chain is a system of organisms linked by trophic connections, Energy transfer between different trophic levels wherein energy is transmitted from the producers (phytoplankton, aquatic plants and algae) Primary consumers, herbivores through the upper trophic layers all the way to the apex predators–birds and mammals in marine ecosystems 10 % Zooplankton feeding on fish. Only about 10 percent of all energy produced at any individual trophic layer

is passed onto the next layer. Because of this significant energy loss, food chains are usually Producers limited to 5-6 trophic layers. 100 % Phytoplankton In the offshore parts of the Baltic Sea, the prevailing type is a relatively simple pelagic Dynamics of sprat and food chain consisting of phytoplankton, planktonic crustaceans (zooplankton) feeding on it, cod stocks in the Baltic Sea plankton-feeding fishes, such as sprats, and predatory fishes, such as cods. Out of the breeding grounds. This had a broad-reaching effect on all trophic layers. The decline of cod population season, offshore areas also host fish-feeding birds, such resulted in the explosion of the Baltic herring and sprat stocks. These reduced the numbers as murres, razorbills, gulls, etc. In coastal waters, trophic of zooplankton, thus indirectly triggering a burst of phytoplankton growth, the so-called 40 20 relations are more complex, comprising a food web consist- “algal bloom”. The increased densities of sprats also intensified their intra-specific competition ing of numerous interlinked alternative food chains. There, for food, resulting in lower weight of individual fish and lower quantities of fat (i.e. energy) 30 15 the diversity of primary energy sources is higher, and the accumulated by them. Some sea birds, such as common murres, are adapted to consume only systems include abundant benthic invertebrates and demer- high energy food, and, as a consequence, significant slowdown in growth of their young was 20 10 sal fish communities feeding on them. The invertebrates are observed. also consumed by wintering sea ducks, while the fishes are 10 5 preyed upon by seals, divers, grebes, sterns, gulls, etc. The Baltic Sea food-chain is very volatile and vulnera- 0 0 ble. In offshore waters, cod is the key species influencing the 1975 1980 1985 1990 1995 2000 2005 dynamics of abundance of many other organisms. Back in the middle of 1980s, cod populations had collapsed because Sprat stocks (1010) cod stocks (108) of overfishing and disrupted recovery of stocks due to Source: ICES 2005a decreased salinity and oxygen deficiency at the spawning

24 THE BOOK OF THE SEA 25 Food chain Parts of the Baltic Sea Ice cover that freeze over in winter

Mild winter

Regular winter

Unusually cold winter

Ice-free part of the Baltic Sea

Ice cover occurs in the Baltic Sea each year. The traces of ice can be found as long as seven months per year, therefore it is very important for physical and ecological conditions in the basin. Due to the low water salinity, the Baltic water starts freezing at the temperatures just below 0 ºC. Ice formation usually starts in mid-November in the northern part of Bothnian Bay and gradually extends southward. The maximum ice cover is reached in February-March, hiding about 45 % of the total sea surface. The Gulfs of Bothnia, Finland and Riga usually freeze Helsinki completely, the edge of ice cover passing near the Stockholm area. To the south of that boundary, Oslo in normal winters ice covers only shallow coastal waters, such as the Curonian Lagoon, Vistula Lagoon, Szczecin Lagoon and parts of the Danish Straits. A complete freeze-over of the Baltic Stockholm Sea happens only in extremely severe winters. The last case was registered in 1947, while in win- Tallinn ter of 1987, ice covered about 96 % of the total surface of the sea. However, even in such extreme conditions, the central part of the Baltic Sea remains open, or the ice cover is very thin there. With the increasing intensity of shipping, ensuring continuous operations of the Riga, Tallinn and other northern Baltic ports is very important. A fleet of some 20-25 icebreakers is engaged in the task. The ports of Klaipėda, Liepaja and Baltijsk are considered as ice-free ports, because the ice cover, if it ever forms there, is thin and shipping is possible without the aid of icebreakers. Riga As the sea ice reaches the thickness of 22 cm, the longest ice road in Europe opens in Copenhagen Estonia. It connects the port of Rohuküla and the island of Hiiumaa stretching for about 26 km. Travelling on ice roads is part of historical and cultural heritage of Estonian islands. Klaipėda The Baltic ice cover is very important to the ringed seal, because these animals are adapted to reproduce on ice. They dig burrows wherein the pups are born and raised. Shrinking of the ice cover, caused by warmer winters in recent decades, poses threat to the survival of this species.

26 THE BOOK OF THE SEA 27 Ice cover Main circulatory routes of water masses Water currents in the Baltic Sea

Surface water masses

Deep water masses

Water masses in seas and oceans are transported long distances by continuous, directional movements of water called currents. Under the influence of the rotation of the Earth, the Baltic Sea currents flow counter-clockwise. The currents passing the south-eastern Baltic coast are heading north and north-east, and their branches diverting towards the Gulfs of Riga, Finland and Bothnia retain general directional trend. They are charged with additional energy by the rivers falling into the sea in these gulfs before returning into the main system of marine currents. Having reached the northernmost part of the Baltic Sea, the currents change their course and flow south towards the Danish Straits along the eastern coast of Sweden. The main factors, causing circulation of water masses, are wind, water density gradient and the flow from the rivers. Winds bring into movement the surface layers of water, whereas the density gradient and associated differences in mass cause turbulence in the deeper layers. The speed of permanent currents in the Baltic Sea reaches only 3-4 cm/s (sometimes up to 10-15 cm/s). During the autumn and winter storms, the velocity of currents may increase significantly, up to 1-1.5 m/s. The deep water currents of the Baltic Sea never flow faster that 3-5 cm/s, therefore fresh water from the Great and the Little Belt may take from half a year to a full year to reach the Åland Islands in the northern part. The maximum current velocity in Lithuanian coastal waters was registered on 11-14 November 1967, in front of Giruliai, at the depth of 33 m. The wind speed then reached 25 m/s and the current velocity was 74 cm/s. The system of Baltic currents is highly dependent on water circulation at the Danish Straits. There, the water movement is rather complicated because of the mixing of fresh and saline water, stratification of the water column, complex contour of the seabed and frequent weather changes. When the weather is still at these straits, the surface layer of the brackish Baltic Sea water flows into the North Sea, while the more dense and saline water from the North Sea flows

along the bottom in the opposite direction. There is no stratification of currents in the Øresund Omstedt et al., 2013 Source:

28 THE BOOK OF THE SEA 29 Water currents strait, because the shallow sills of Drogden and Darss hinder the inflow of denser water from the North Sea into the Baltic Sea. However, the situation may change under the strong western or south-western winds, because they might cause significant flow of the North Sea water resulting in the water surge at Skagerrak and Kattegat, and as a consequence, saline water may sweep into the Baltic Sea not only along the bottom but through the entire cross-sectional area of the straits, also rolling over the Drogden Sill and the Darss Sill. A reverse process is also possible, when prevailing eastern winds cause water surge on the Baltic side. The Curonian Lagoon water level is usually higher than that of the Baltic Sea, therefore prevailing current in the Klaipėda Strait is flowing outward, carrying fresh water masses from the lagoon into the sea. Under gale-force northern or north-western winds, the current shifts The realms of the its direction because of the surge of the Baltic Sea waters, and the brackish water whooshes into the lagoon. In extreme cases, the sea water may reach as far as the Cape of Ventė or the town of Nida, forcing the freshwater fish of the Curonian Lagoon to retreat. It is quite likely, Baltic Sea however, that this retreat of fish is mostly caused by the lower temperature of incoming water, rather than by its higher salinity. Currents are of great importance. They ensure circulation and mixing of huge water masses thus changing the distribution patterns of salinity and oxygen concentration. Currents also participate in coastal formation and some even in climate formation processes, they transport nutrients and marine organisms lacking active mobility.

30 THE BOOK OF THE SEA 31 Water currents The swash zone

This is the borderline of the marine world. To us, the sea begins here, while to the marine inhabitants here it ends. To many holiday makers, this world reminds promenades on the beach with the waves gently tickling their bare feet, while they scan the shore with their eyes in attempt to spot a piece of amber or some other sea treasure among shiny pebbles, shells washed ashore, piles of fancy seaweeds and polished shards of glass. Treasures do exist there. However, a very few people have heard of them and even less have actually discovered them.

32 THE BOOK OF THE SEA 33 The swash zone 34 THE BOOK OF THE SEA 35 The swash zone The swash zone is the most volatile part of the beach, where the waves breaking against the shoreline carry sand and create a link between the beach and the sea. B A Measured from the shoreline up, the swash zone may encompass up to 20 m of the beach during storms, while in the calm weather it would shrink to a mere few cen-

D timetres. In spite of that, the traces of previous storms are almost always present around: little pools, washed ashore gravel, piles of seaweeds and shells, and some C rubbish, accidentally swept from ships or thrown into the sea by people. Because of recurring storms and irregular flooding, A Black-headed gull when the same part of the beach becomes either sub- B Common tern merged or dry, the swash zone might appear to have C Amber neither characteristic fauna nor flora. Only occasional- D Black carrageen ly, usually right after storms, one can see with a naked eye a few “emigrants” from the sea–amphipods, washed ashore together with the clusters of seaweeds, ripped by the storm from boulders on the bottom. Even rarer sighting on the sandy beach are the only macroscopic leaping crustaceans, adapted for permanent life in this zone, also called “sand fleas” (Talitrus saltator). A very few visitors coming to enjoy the beach Sand hopper, also known know that deep underneath (0.3 m deep in summer and up to 0.5 m in winter) entire as the “sand flea”, sitting in colonies of these crustaceans may be thriving. In the safety of night, when predators its burrow are absent, these arthropods would usually crawl to the surface to feed. Those, thinking that the swash zone holds nothing else but sand and some sea sediments, would be surprised to learn, that among particles of sand, where

36 THE BOOK OF THE SEA 37 The sswwashash zone zone Coarse sand with some Bladder wrack gravel granules and pebbles. (Fucus vesiculosus, Linnaeus, 1753) The latter consist of hard crystalline rock particles The bladder wrack is a khaki-coloured brown alga, abundant of relatively high resistance on the rocky shores where it grows attached to hard substrates. to mechanical destruction In the Baltic Sea, it is most abundant near the Swedish and Finnish coasts. This brown alga does not grow in Lithuanian Well separated medium coastal waters because of strong swells during storms, howev- sand with prevailing quartz er, one may find beached fragments of bladder wrack brought particles by the sea from other areas. The frond is flat and branching, and it usually holds numerous spherical air bladders. These bladders help the fronds to float closer to the surface and increase the overall surface area important for photosynthesis. Dependent on the temperature, impact of waves and currents, and the luminance at the bottom level, the growth rates of bladder wrack may vary between 0.05 and 0.14 cm/day, the In eastern countries, bladder wrack also is a common moisture is captured, dwell rich communities of tiny animals, usually smaller than 0.5 maximal length reaching about 2 m. The life span is 4-5 years. food ingredient. The main active substance produced by mm across. They are also known as meiofauna. The diversity of these little organisms Dense fields of bladder wrack provide an important sub- bladder wrack is alginic acid, used by the food industry as might in some cases be up to 25 times higher than that of macroscopic organisms strate and shelter to other species, including malacostracans a natural thickening agent for drinks, ice creams or soups. seen with a naked eye. These animals exploit the cavities existing between sand (or higher crustaceans), worms and snails. particles, whose volume may account for up to the 40 % of the total volume of sand. Since 1811, Fucus vesiculosus has been renown as one of Sand hopper Such communities play a unique role by decomposing the organic matter accumulat- the key sources of iodine, which is necessary for the pro- (Talitrus saltator, Montagu, 1890) ed in the sand, and thus making an invisible contribution to the clean-up of beaches. duction of hormone thyroxine, and it has been used to treat In winter, as temperatures drop below zero, even the scarcely observed life multiple conditions, such as thyroid disorders, inflammation Talitrus saltator is a terrestrial amphipod widespread in disappears from the swash zone, while the animals that hide in the sand retreat into of joints, etc. These macroscopic algae are a valuable source north-eastern and northern Atlantic, Baltic and Mediterra- deeper layers. Sometimes air temperature is the only factor determining the location of many other important micro elements: calcium, mag- nean regions. They are most common at the tidal zones of of the swash zone for the next spring. Ice cover along the shoreline protects the sand nesium, sodium, potassium, iron, chromium, zinc, as well sandy beaches, where they dig 10-30 cm deep into the sand against strong storms quite efficiently, increasing probability that the swash zone will as vitamins A, C, E, B, etc., therefore bladder wrack is used during the daytime to avoid dehydration (desiccation), while remain unchanged. However, in warm winters sandy beaches can be heavily eroded by beauty industry as a substance regulating skin elasticity. at night they resurface to feed on decaying algae or other by powerful storms, so the next season both the swash zone and all its associated A Japanese study, carried out in 2005, revealed that blad- macroscopic plants washed ashore. communities develop in new locations, although the key species and their interac- der wrack can suppress the production of hormones which These dull brown or greenish amphipods have one pair tions with the environment remain the same. Only a handful of holidaymakers would increase the risk of breast cancer. of black eyes, and two pairs of antennae, one of them being have sufficient knowledge of the swash zone to notice the difference.

38 THEJŪROS BOOK KNYG OFA THE SEA 39 The swash zone ever taken a ferry to cross to Smiltynė (Curonian Spit)–most of the birds following the boat would be the black-headed gulls. In summer, the best identifiers of this species are dark brown head and dark red legs and beaks. Beyond the breeding season, the dark head colouration is lost, only a few dark spots remain, especially around the ears. During migration and in winter, the diversity of gull species increases, especially at the sea coast–up to 10 dif- thicker and longer than the other. The females are slightly ferent species can be observed then. The identification of smaller than the males. different gull species requires some skills, as their overall Talitrus saltator is sometimes known by its popular name appearance is usually very similar, the differences being in of the “sand flea” because of its leaps sometimes reaching the size, the colour of legs and bills, and the behaviour. Juve- almost 1 m, produced by a flexion of the abdomen. The nile birds are even more difficult to distinguish, because they direction of leaps is not controlled, therefore sand fleas usually take several years to attain the appearance of adult birds. repeat a sequence of several leaps in order to escape into safety. Nocturnal migration of sand hoppers (or sand fleas) Common gull deeper into the dry land, where they feed on decomposing (Larus canus, Linnaeus, 1758) algae, is most active a few hours past midnight and continues till sunrise. There is scientific evidence that amphipods use the The common gull is a usual visitor at the coastal area during position of the Sun and the Moon to assess the time of the day. migration and in winter, but it also breeds in Lithuania. This The highest density of terrestrial amphipods on the species is broadly widespread in the whole of Eurasia and Lithuanian coast is observed in September, reaching some western part of North America. In Lithuania, it breeds in low 280 adult individuals per square metre. numbers in different parts of the country, somewhat bigger colonies settle on the island of Lake Kretuonas. In winter, Common gull Gulls it is common at the Lithuanian coast. Feeds on various invertebrates and small fish, both at sea and on land. As Almost 20 gull species have been registered in Lithuania, but many other gull species in Lithuania, the common gulls may about a half of these are only casual migrants. Only five spe- often turn to scavenging at landfills. The size is significantly cies of gulls breed regularly in our country, the most abun- larger than that of the black-headed gull, from which it also dant of them being the black-headed gull (Chroicocephalus differs by greenish-yellow bill and legs. During the breeding ridibundus), breeding in large colonies in different parts of season, the head of the common gull is bright white, while in the country. This species is well familiar to those who have autumn and winter it turns greyish with some spots.

40 THE BOOK OF THE SEA 41 The swash zone European herring gull Great black-backed gull (Larus argentatus, Pontoppidan, 1763) (Larus marinus, Linnaeus, 1758)

Another regular gull species in Lithuania is the European The largest of all gull species regularly encountered at the herring gull. The range of this species spans from the Kola Lithuanian coast and one of the largest gull species world- Peninsula and northern parts of Norway in the north to wide is the great black-backed gull, whose wingspan may the French coasts of the Atlantic Ocean in the south. The reach 1.7 m. It differs from the European herring gull not first breeding pairs were registered in Lithuania just over 30 only by its size, but also by much darker back and upper side years ago on Kiaulės Nugara Island in the Curonian Lagoon. of the wings. Since then, the number of breeding pairs has been gradually Another typical marine gull species worth mentioning is increasing, and at present some 200 pairs of the European the black-legged kittiwake (Rissa tridactyla). This bird does herring gull breed all over the country. At the seaside, this not breed in the Baltic Sea area, however, lately it has become Sandwich tern species is common both during the migratory and wintering a rather common visitor. The first sighting in Lithuania was seasons. The European herring gull is somewhat similar to the registered in 1982. This species is seldom seen from the shore, common gull, but is much bigger, has a more massive yellow being a typical offshore (pelagic) species, spending somewhat beak with a red dot on its lower mandible, and pink legs. Two more time on land only during the breeding season. In Eu- other gull species related and very similar to the European rope, it breeds on the shores of the North Sea, Atlantic Ocean herring gull are also found in Lithuania: the Caspian gull and Barents Sea, usually gathering in huge colonies on the (Larus cachinnans) also breeding in Lithuania in low numbers, coastal cliffs where the nests lie less than a metre apart. Their sometimes together with herring gulls, and the yellow-legged prevailing food are marine invertebrates and fish. gull (Larus michahellis) which does not breed in Lithuania but The little gull (Hydrocoloeus minutus), as suggested by is a regular visitor. its name, is the smallest gull species not only in Lithuania, but also worldwide. This species is a rare breeder in our Juvenile European herring gull country included in the national Red Data Book and also protected in the entire European Union. At the seaside, it is often observed on migration, in late July–August. Migrating birds are easy to recognise by their dark underwings, round- Great black-backed gull ed wing tips and light undulating flight pattern, especially during foraging, when the birds pick various invertebrates from the sea surface. During migration, these birds will have already shed their black hoods which distinguish them in the breeding season.

42 THE BOOK OF THE SEA 43 The swash zone Terns Sublittoral sandy slopes The most common and most known tern species in our country is the common tern (Sterna hirundo), although its relative, the black tern (Chlidonias niger), is equally abundant. Up to several thousand pairs of common tern breed in Lithuania. Usually they nest in small colonies on islands and islets of lakes, ponds and rivers. They feed exclusively in water, the main prey being small fish, less often–aquatic invertebrates. While foraging, terns often plunge into the water from flight, Although this realm is hidden under the water, the thus reaching prey a few decimetres below the surface. Because of slightly similar appearance, behaviour immediate associations flashing the images of the and habitats, terns are frequently mistaken for gulls, and vice-versa, especially the common tern and the most wide- Common tern Baltic sand dunes are not tremendously misleading. spread black-headed gull. However, these two birds are not so difficult to recognise, both on the ground and in flight. Another tern species, the Sandwich tern (Sterna sand- Some of those submarine sandy slopes used to Looking at a perching bird, terns are distinguished by their vicensis), can also be observed on migration at the Lithua- shorter legs and prolonged body shape due to long wing nian coastline in late summer, July to August. Up to several be parts of the developing Baltic coasts several and tail feathers. A flying tern appears more gracious, with hundred migrating individuals are usually registered within its wings longer and narrower than those of a gull. The bill a season. millennia ago. In this realm, just as in the dunes of of a tern is longer and sharper than that of a gull. It is also The Sandwich tern is a large tern species among those worth noting that no terns are found in Lithuania in winter– observed at the Lithuanian coast, yielding in size only to the dry land, the apparently boring sandy surface they are long-distance migrants wintering in the southern the Caspian tern (Hydroprogne caspia) from which it clearly hemisphere. At the Lithuanian seaside, migrating common differs by a slender dark beak with a light tip (the beak of may share many interesting secrets with those who terns are quite numerous from the end of summer and Caspian tern is bulkier and bright red). It is worth noting, through September. At the same time, another close relative that this tern species does not breed in Lithuania, and its take a closer look and dig a little deeper into the of the common tern – the Arctic tern (Sterna paradisaea) breeding range pattern in Europe is highly fragmented. – can also be seen. The main difference between the two upper layer of sand particles. species is the longer external tail feathers (rectrices) of the Arctic tern, giving its tail a deeper forked appearance. The migrating common terns are usually observed in their winter plumage with a paler “hood” and darker beak.

44 THE BOOK OF THE SEA 45 Sublittoral sandy slopes 46 THE BOOK OF THE SEA 47 Sublittoral sandy slopes A B

C The sand that we see on our beaches is not so widespread on the bottom of the sea– the Baltic seabed is predominated by boulders, rocks, clay and silt bottoms. Under- water sandy slopes are common only in the south-eastern parts of the sea, in the H D Lithuanian, Latvian, Polish and German coastal waters. In the most shallow part, ac- E F cessible to swimmers, sandy bottom is easily recognised by sand ripples shaped by G currents and waves that constantly move the sand. Somewhat deeper, the ripples turn into larger sand bars reaching several metres in height and stretching along the shoreline, that are also known as sandbanks. In differ- A Red-throated loon E Small sandeel ent segments of the sublittoral zone, at the depths of B Razorbill F Relict isopod crustacean Saduria entomon up to 10 m, the number of these sandbanks and the C Baltic herring G Brown shrimp troughs separating them varies and they constantly D European flounder H Opossum shrimps change their position and height. In this zone, where the impact of waves is felt all the way to the bottom, sandy banks are not very suitable for marine life. For species adapted to burrowing in the sand or anchoring in it by their roots, the bottom may be too unstable as the sand moves most of the time. Organic deposits are also scarce, dispersed by the waves during storms, therefore only mobile animals capable to move in from Variety of benthic organisms deeper areas are able to feed there, such as small amphipods, juvenile flatfish, and and traces of their activities the brown shrimps. In calm summer nights these areas become a feasting ground on the sea bottom for young flatfish. They arrive in big numbers to feed on abundant colonies of amphipods. With the break of day, the amphipods disperse to the nearest shelters, while the flatfish retreat into deeper waters.

48 THE BOOK OF THE SEA 49 Sublilittttoraloral san sandy dyslo slopes pes In the deeper parts of sandy slopes, the impact of waves is less obvious and the Baltic macoma are also consumed by sea ducks foraging on benthic inverte- seasonal variation of temperature and other living conditions is smaller. Observa- (Macoma balthica, Linnaeus, 1758) brates, such as velvet scoter. tions by diving or underwater cameras usually show only individual flatfish or gobies, The shells of Baltic macoma are easy to find on the however, a closer inspection would reveal thousands of small burrows, sandy tubes The Baltic macoma is a small marine mollusc with an oval beach. Since their growth rate is lower in winter and higher and protruding siphons. The apparently empty sandy slopes and plains actually hide shell featuring distinctive growth rings. The colour of shells in summer, the shells display a pattern of growth rings which a rich world, wherein life activities are concentrated in the thin surface layer of sand may range from pink or whitish to pale yellow or even allow to determine the age of an individual. Usually maco- 1‑2 cm deep. Although oxygen does not penetrate deep into sand, the largest benthic orange. The colouration of this clam is known to depend on mas live for 5‑10 years. organisms can burrow as deep as 20‑30 cm. They survive by extending to the surface its habitat, nutrition and water currents. The shells of the off- long siphons used to pump in water and food, or by moving actively in their burrows shore individuals are usually thicker and brighter, whereas Sand gaper and thus inducing water circulation and replenishment. Regardless of how deep this those living in shallow waters tend to have bigger but thinner (Mya arenaria, Linnaeus, 1758) world reaches into the sand, its inhabitants–bivalve molluscs, priapulid worms and and paler shells. various polychaetes–are the main source of food for demersal fishes and sea ducks, Baltic macoma lives buried in the surface layer of sedi- The sand gaper is the first invasive species in Europe. It is such as the velvet scoter. ments and feeds by protruding long and adjustable siphons thought to have been brought as early as 13th century from The sandy slopes might appear mostly unchanging, but only from the per- which could be up to 10 times longer than the length of the North America, along with the boulders used by Vikings as spective of a human lifespan. The tree stumps, found in these zones within the shells. Dependent on its habitat, Baltic macoma may use a ballast for their boats. Lithuanian coastal waters of the modern Baltic Sea, at the depths of some 27 m at different feeding strategies. Macomas living on shallow sandy Sand gaper has a very thin and fragile calcium car- Juodkrantė and 14 m at Melnragė are the proof of extensive pine forests that were substrates filter out their food from the water column with bonate shell which can reach up to 15 cm in length. The once growing there about 11-9 thousand years ago. Back then, the water levels were the help of these siphons, whereas those inhabiting deeper colour of the shell ranges from dull pink to grey. Sand gapers significantly lower and the territories presently covered by the sandy slopes were and silty bottom areas use them to suck in small particles of usually live burrowed some 15-25 cm deep into sand or sill. part of the coastal areas. decomposing organic matter from the surface of the substrate. Because of its physiological adaptation, sand gaper can live It is the most widespread invertebrate species in the Bal- in a broad range of temperatures ranging from -2 °C to 28 °C tic Sea. To flatfish, macoma is the key source of food. They and tolerate very low salinity. The spawning takes place twice a year, when the molluscs release into the water millions of floating eggs which turn into larvae in about 12 hours. The larva stage lasts for 2-3 weeks, when they drift at the water surface before sinking to the bottom as tiny molluscs of some 0,2 mm. Sand gapers reach maturity between the 1st and 4th year of their life. Their life ex- pectancy is relatively long, 10-12 years, the maximum registered age being 28 years. Because of its longevity and easy identification, this mollusc is used as a bioindicator for the assessment of environmental status in the entire region of the Baltic Sea.

50 THEJŪROS BOOK KNYG OFA THE SEA 51 Sublittoral sandy slopes Sand gaper feeds on microscopic plankton (diatoms, Cockles are typical inhabitants of the intertidal zone, bacteria and other tiny organisms) as well as on decom- but the Baltic species is adapted to permanent life on the posing organic matter which are captured by filtration. sublittoral slopes. Its close relative, the common cockle The molluscs burrow into the substrate and then stick (Cerastoderma edule), is a favourite seafood in many West out to the surface a specific tubular organ–siphon. One European countries. Their popularity as a seafood is caused of its openings is used to suck water in, then, as all useful not only by their excellent taste but also by high abundance content is absorbed, the surplus water is ejected through (for instance, in the North Sea the density of certain popu- another opening. An adult sand gaper is capable to filter lations may reach 10 000 individuals per sq. m). As they are Sand gaper over 50 l of water per day. filter-feeders and live in proximity to human populations Sand gapers are preyed upon by demersal fish and (for instance, in sea bays), they might pick up some path- diving sea birds. ogenic organisms, e.g. the intestinal bacterium Escherichia The empty shells are beached by the waves, so they can coli. Therefore the European Commission has set specific be found while walking along the shore. requirements on the treatment of these molluscs intended for human consumption. Lagoon cockle Cockles are found in the Mediterranean, Caspian, Black and (Cerastoderma glaucum, Bruguière, 1789) North Seas. They are sensitive to chemical pollution and disappear from strongly contaminated waters. Lagoon cockles are filter-feeders living burrowed into soft substrates in the shallows. Their larval stage encompass 11th to 30th days of their life spent in the open sea, then the young individuals produce special byssal threads to attach themselves to filamentous algae before they burrow several centimetres deep into the bottom. The spawning takes place in May-July. Lagoon cockles live for about 5 years and reach the size of 1.5 cm in the Baltic Sea. Lagoon cockles have a rounded shell with 22-28 radial ribs and, perpendicular to them, clearly visible embossed growth rings. These rings, which reflect the differences in growth rates during cold and warm seasons, can be used to determine the age of cockles. The colour of shells ranges from white, beige or yellow to dark brown. Some individuals may feature small blue spots.

52 THE BOOK OF THE SEA 53 Sublittoral sandy slopes Brown shrimp Lithuanian coastal waters are relatively smaller than those from predators while at night they actively swim in the water and cold lakes of the glacial origin. Curiously, it is consid- (Crangon crangon, Linnaeus, 1758) living in normal sea water but they are still suitable for hu- column. There are references, suggesting that in some re- ered extinct from the Lithuanian inland waters and listed in man consumption. We might not be used to eat our shrimps gions of the northern Baltic Sea the abundance of M. affinis the national Red Data Book under category “0”. However, in The brown shrimp (also known as the common shrimp or because of their small size, but they are popular food source follows a fluctuation pattern with 6-7 years cycle. The causes the Baltic Sea, it is a relatively common species in the appro- sand shrimp) is the most abundant shrimp species of sandy for gulls, terns and demersal fish. of this fluctuation are not yet understood. priate habitats. coastal zones, wherein their numbers in summer season The brown shrimp is one of the key commercial species The species is very sensitive to hypoxia and contamina- might reach up to 60 individuals per sq. m. These shrimps harvested in the North Sea. The biggest catches are landed by tion, therefore it is a perfect indicator of good water quality. Relict isopod crustacean burrow into the sand during daytime to avoid strong surf or the Dutch and German fishermen. Throughout its entire life cycle, which lasts 1-3 years, (Blyškusis jūrvėžys in Lithuanian) predators and to ambush their own prey. At night, they set for The curious and observant holiday makers might get M. affinis breeds just once. The mating takes place in (Saduria entomon, Linnaeus, 1758) active hunting. The brown shrimps are not very picky about a glimpse of these shrimps, while wading in the shallow sea autumn, while in spring the females produce some 20-30 food. They forage on algae, various larvae and molluscs. In the waters. offspring. Saduria entomon is a relict of the last glacial period who Baltic Sea, the species grows 3-5 cm long, while in some other These amphipods fall prey to demersal fishes, such as migrated from the Barents Sea into the Baltic Sea more seas they might even reach 9 cm. Being that big, they are Relict amphipod flatfish, and the isopod crustacean Saduria entomon. than 12.5 thousand years ago. Its distribution range has capable to prey even on smaller fish. The females are relatively (Monoporeia affinis, Lindström, 1855) The specimens of this species are not to be seen on the been changing over time, sometimes shrinking, sometimes bigger than males. The latter mate only once in the lifetime, beach. They can only be inspected in deeper seabed samples expanding, but nowadays the species is spread all over the thereafter they change their gender and become females. The This species is a relict of the last glacial period which collected by scientists. M. affinis can also be found in deep Baltic Sea. Because of successful adaptation to a broad gender transformation lasts for about two months. The aver- inhabits the soft bottom substrates of both fresh and saline age life span is 2-3 years. As all other crustaceans, the brown water bodies. It lives at the depths of 40–60 m, where the shrimps undergo ecdysis while growing. At higher water population density might reach some 10 000-20 000 indi- temperatures, the process reoccurs every 8-9 days, and the viduals per square metre. This small (8 mm) relict amphi- shrimps gain 1-3 mm in size after each round. pod, formerly referred to as Pontoporeia affinis, does not In summer, the females carry under their abdomens have a common name in the Lithuanian language. M. af- some 4 500 eggs which take 4‑13 weeks to hatch. finis plays an important role in mixing bottom sediments. Because of the low salinity of the Baltic Sea and sea- By digging into the substrate in search for organic material, sonal temperature fluctuations, the shrimps living in the these amphipods promote circulation and exchange of various substances between the bottom sediments and deepest water layers. Amphipods of the Monoporeia genus perform active nocturnal migrations within the water column. In other parts of the Baltic Sea, where this species occurs in more shallow waters, it also demonstrates vertical migrations following the daily cycle. In daylight, they hide in the substrate Relict amphipod Monoporeia affinis

54 THE BOOK OF THE SEA 55 Sublittoral sandy slopes salinity range (from 1 to 20 ‰), S. entomon is also found in Small sandeel Lake Ladoga and at least 8 Swedish lakes. (Ammodytes tobianus, Linnaeus, 1758) Most likely due to external resemblance, in Lithuania it has another vernacular name that translates as the “sea The small sandeel is widespread in the North Atlantic, from cockroach” (Locally applied to a few other crustacean species Murmansk down to Spain, including Iceland, the Baltic Sea, in different countries. [Translator’s remark]). as well as the Mediterranean Sea. At the Lithuanian coasts, This species is one of the largest crustaceans of the Baltic they are common in sandy shallows and rarely seen in the Sea. The largest, 9 cm long specimen was found in the Gulf offshore waters. Sandeels usually swim in shoals, sometimes Relict isopod crustacean Saduria entomon of Bothnia. The females usually reproduce just once in their very close to the shoreline. They spend significant share of 3-4 year lifespan, because after the spawning they tend to die time burrowed in the sand. In winter they are inactive and of exhaustion. hide in the sand, burrowing up to 20-50 cm deep. S. entomon does not tolerate warm water, so it retreats into Sandeels feed on zooplankton, crustaceans, worms, the deeper areas in summer. These isopods inhabit broad range sometimes also on juvenile fish. They themselves fall prey to of bottom substrates: sandy plains, boulder accumulations, bigger predatory fishes, such as cods, turbots, eels, occasion- morainic deposits or silt sediments, wherever demersal fauna ally even flounders, and the juvenile small sandeels are also is rich. They crawl on the seabed leaving distinctive trails. If eaten by the Baltic herrings and great sandeels. Quite many necessary, these isopods are also capable of swimming in an sandeels are captured by fish-feeding sea birds. upside-down position, although this is not a typical behaviour. The small sandeel is a typical fish of the Baltic coastal S. entomon is a predatory species, preying upon benthic waters, similar to a much rarer species, the great sandeel animals, usually other smaller invertebrates. They are also (Hyperoplus lanceolatus). The body of this small fish considered as cannibals capable of feeding on their own reaching 10-15 cm (max. 25 cm) is elongated and covered species, or scavenging for any other decaying flesh. They in tiny scales. The dorsal fin is very long, the anal fin is themselves fall prey to commercially important Baltic fishes, shorter by half, the pectoral fins are small, and the pelvic such as cod or flatfish. fins are absent altogether. The dorsal part is greenish-blue,

56 THE BOOK OF THE SEA 57 Sublittoral sandy slopes the sides bear a shade of yellow, while the belly is silvery. floating larvae enable turbots to disperse far away from the different salinity levels and is abundant at the Lithuanian The lower jaw does not have large teeth and is protrud- original spawning grounds. coast, often entering also freshwater bodies, such as the ing forward, the mouth is wide. When this fish opens Turbot is one of the most valuable commercial fish spe- Curonian Lagoon or some river estuaries in other coun- its mouth, the latter folds out like bellows. The lifespan cies living in the Baltic coastal zone. There is some evidence tries, where they may migrate significant distances up- reaches 10 years. that seaside dwellers in the current Lithuanian territory were stream in search for food. They are most common on sandy Small sandeels reach sexual maturity at the age of 1-2 already using turbots for food as early as 3 000 B.C. Turbot bottoms, up to 50-60 m deep. The juvenile fish usually stick years and spawn in summer or late autumn in the coastal is a slow growing fish, often subject to over-exploitation due near the shore, while the big adults retreat into the deeper waters up to 30 m deep. The females produce 4‑22 thousand to the high demand, therefore the stocks are declining in areas. eggs with the diameter of 0.8‑1.0 mm, released in small many areas. The most popular fishing method is by nets in The young feed on zooplankton, insect larvae, or clusters onto the sandy bottom. The larvae are 4‑8 mm long the coastal waters before the spawning. This valuable fish small crustaceans, later switching to molluscs, worms, and swim in the water column until they turn into fry upon may be cooked in many different ways; turbots can be grilled shrimps and fish or their young as they grow bigger. reaching 20 mm in size. or stewed spiced up with different seafood, mushrooms, Adult flounders are a difficult catch for other predatory Sandeels are used by humans as a bait for fishing larger wine, vermouth or champagne. fish, such as cod, because of their body shape, so mostly species (cods, eels, turbots, flounders, etc.) as well as for the young turbots sometimes fall prey to cods while the adults juvenile flounders fall prey to them. Smaller founders are production of fish protein powder. may serve lunch to seals. European flounder sometimes grabbed by cormorants, while the big ones are Turbot is a flat, almost round-shaped fish. The “dorsal” (Platichthys flesus, Linnaeus, 1758) hunted by seals. Turbot side of the body where both eyes are situated is not covered The body of the European flounder is asymmetric, (Scophthalmus maximus, Linnaeus, 1758) in scales but features harsh osseous bumps. Turbots are The European flounder lives along the north-eastern Atlan- oval-shaped, flat on the sides. The lateral line is surrounded capable to adapt the colour and pattern of their upper side tic coastline, from the White, Barents and Baltic Seas down by little spikes, situated at the anal part and the basis of the The turbot is a typical marine fish species widespread in the to the background, which makes these masters of camou- to the Mediterranean and Black Seas. This species tolerates dorsal fin–this is an important identifier, enabling to distin- north-eastern parts of the Atlantic: in the Mediterranean flage difficult to spot to both humans and their prey–other guish it from another similar species, the European plaice Sea and along the European coastline all the way up to the fish. The downward facing side is usually white, although (Pleuronectes platessa), which is rare in our waters and does Polar Circle, including the Baltic Sea. Turbots prefer sandy, sometimes it bears pigmentation spots. The mouth of this not have such spikes. The upward facing side is brown or rocky or mixed-type bottoms and they easily tolerate the low typical predator is very wide, adapted to swallowing rather khaki coloured with brown or orange spots, so it blends well salinity of the Baltic waters. big prey. Turbots may reach 25 kg, although in Lithuanian with the colours of the substrate. This enables flounders to Adult turbots prey on other demersal fish, such as waters they are significantly smaller, usually under 1 kg, and camouflage well and avoid detection. The downward side is sandeels, gobies, or Baltic herrings, less often they also only exceptional specimens weigh 7 kg. white, sometimes with spots. The mouth is small, with small include in their ration crustaceans and bivalve molluscs. The Turbots normally live away from the shores, but in teeth. In the Baltic Sea, flounders can reach 45 cm and 1.2 kg, hatchlings, like those of other fish species, start feeding on spring they arrive to the coastal shallows well before the although the usual size is 20-30 cm. zooplankton, eventually switching to benthic invertebrates. actual spawning. The spawning happens in batches in May- European flounders reach sexual maturity at the age of Because of their body shape, turbots are difficult to cap- June, the overall fecundity may range from 0.5 million to 3-4 years, and they spawn in March-May in the coastal waters ture for other predatory fish or fish-feeding birds, however, full 14 million tiny floating eggs. These eggs and the hatched or deeper water areas. There are opinions that two varieties of

58 THE BOOK OF THE SEA 59 Sublittoral sandy slopes flounder exist and they even show some genetic differences: of the velvet scoter. Within the last two decades, however, the eggs of flounders spawning near the coast sink to the bot- the wintering stocks of this species have declined by about tom, while those of the specimens spawning in the deep zones 60 %, the latest counts suggesting some 370 000 birds. The are buoyant, i.e. they float in the water column. The fertility main threats possibly responsible for such dramatic decline is 0.4‑2 million eggs. The hatchlings have their eyes on both are oil pollution, accidental catches by various fishing gear sides, but as they grow, they undergo metamorphosis and and eutrophication. The global warming could have caused their eyes move onto one side–the juveniles are about 10 mm a certain shift of the wintering grounds, however, this long by that time. possibility has not been properly explored yet. The species Archaeological data suggest that flounders were used for was included into the IUCN Red List of Threatened Species Velvet scoter food by the coastal dwellers as early as 6 000 B.C. in the cur- in 2012. rent German territory, some 5 thousand years ago in Estonia Abundant aggregations of scoters in the Baltic Sea are and some 3 thousand years ago in Lithuania. Nowadays observed in Pomeranian Bay, the Irbe Strait, the Gulf of Riga flounders are important part of the commercial fishing in and along the Lithuanian and Latvian coastlines. The largest the Baltic Sea, usually fished by trawls or other nets. In Lith- aggregations in Lithuania are observed in front of the Curo- uania they are usually fried, sometimes smoked, and their nian Spit where sandy seabed is prevailing. Individual birds fillet can be used by experienced chefs in variety of dishes to can be seen in the inland water bodies. please even the most demanding taste. When in the sea, velvet scoters are found not only in the shallow coastal waters but also offshore, in much deeper Velvet scoter areas reaching up to 30 m. In the last few years, new big (Melanitta fusca, Linnaeus, 1758) offshore aggregations of almost 30 000 individuals were also observed in the area of Klaipėda–Ventspils Plateau in front Common scoter This is a northern bird species. It breads in the inland waters of the Lithuanian coast. of taiga and forest tundra as well as at the coasts of the Arctic As many other diving sea ducks, velvet scoters are ben- seas. The breeding range includes also some Baltic coastal thic feeders–they forage on molluscs and other invertebrates, states: Estonia, Sweden, Finland and Russia. The wintering often digging them out of the soft substrate. grounds are in somewhat more southern seas: the North, Baltic and Norwegian Seas. The wintering birds ringed in Common scoter Lithuanian waters were registered breeding in the northern (Melanitta nigra, Linnaeus, 1758) part of Russia, from the Arkhangelsk administrative district in the west to the Taimyr Peninsula in the east. At the first sight this sea duck is very similar to the velvet Some 20 years ago, the wintering grounds in the Baltic scoter. The main difference from the latter is the absence of Sea used to attract about 93 % of the regional population a white speculum on their wings in both male and female

60 THE BOOK OF THE SEA 61 Sublittoral sandy slopes common scoters. This identifier, however, is only seen when This species can be seen both at the Curonian Lagoon coast the birds take flight. and near Palanga. The flocks are usually denser that those Reefs As many other sea ducks, the common scoter is a north- of the velvet scoter. Their favourite wintering grounds are ern species wintering in more southern seas. Contrary to the shallow coastal waters with the depths not exceeding 15 m. long-tailed duck and the velvet scoter, the common scoter Separate individuals can be noticed in the inland waters. can breed further away from freshwater bodies, wherever it Their main food are molluscs but other invertebrates are finds a suitable shelter to hide the nest (under some tundra also eagerly picked up. shrubs, in tall grass, etc.). Within the last 20 years, the Baltic wintering stocks The largest wintering aggregations in the Baltic Sea are of the common scoter have declined almost by half. This registered in the western part of the sea, in Polish, German decline is explained by certain breeding failures in their It may sound incredible, but reefs do exist in the and Danish waters; Kattegat attracts especially numerous northern breeding grounds, as well as by risks at the winter- flocks. In Lithuanian waters, the wintering population is ing areas: accidental catches by fishing gear, oil pollution and Baltic Sea! They might be less colourful that the sparse, with just a few hundred individuals registered annually. eutrophication. famous coral reefs, but that does not make them less interesting or valuable. It takes more than just diving into the sea to discover the treasures and bright colours of these reefs–you would need some good luck. You have to wait for the clear offshore water and a bright sunny day. And then it would be entirely up to you to find the right spots where the reef reveals its secrets...

62 THE BOOK OF THE SEA 63 Reefs 64 THE BOOK OF THE SEA 65 Reefs Reefs are submerged oases supporting huge variety of bottom animal and plant species. The hard substrate offers excellent conditions for seaweeds to attach, while a complex bottom structure provides numerous hideouts and shelters for animals to hide. Seaweeds attract highly diverse animals who use algae as a food source, breeding grounds or hiding places. A Although in other seas the prevailing reefs are of biological origin, built by the coral polyps or soft corals, the basis of the Baltic reefs is made of rocks or boulders. In Lithu- anian waters, the boulder-based reefs are most common. In shallow waters up to 15 m I deep, where light still reaches the bottom, the boulders are usually covered in vegeta- K C tion. At some locations, the bottom relief creates areas sheltered from waves, therefore D B bottom seaweeds become so dense that they leave no space for benthic animals to at- J tach to the boulders. Such thickets, especially those made of the black carrageen, a per- G L F N ennial red seaweed, are important spawning grounds of the Baltic herring. The eggs laid H E on the thalli of red seaweeds are thought to have especially favourable development M conditions, while the fry finds a lot of hideouts from the swell and predators. Reefs can vary greatly according to their form and A Long-tailed duck H Round goby benthic communities evolved on their basis. Quite B Steller’s eider I Spawning Baltic herring recently, merely a decade ago, unusual underwater C Great crested grebe J Baltic herring eggs on black carrageen ridges were discovered near Palanga; they reach 5 m in D European eel K Black carrageen meadows height, are narrow and stretch for a few tens of metres, E Lumpfish L Baltic isopod with their slopes steep like walls. These ridges consist F Shorthorn sculpin M Mussels of especially hard type of clay, covered in mussels and G Eelpout N Bay barnacle hydroids, and they are usually found in clusters at the depths of 15-17 m. The ridges are thought to have formed more than 130 000 years ago. These unique structures were noticed when modern multibeam echosounders were applied in depth measurements. Boulders at the Lithuanian Precise maps of the ridge distribution along the Lithuanian coast were produced coast, at the depth of 8 m with the help of these echosounders. Until now, similar ridges shaped by glaciers have been discovered worldwide only in the Scottish waters, and in the Baltic Sea this remains the only location of such unusual reefs. The ridges have become a favourite spot among diving enthusiasts.

66 THE BOOK OF THE SEA 67 Reefs Reef distribution In the deeper areas, where the light is limited or the seabed conditions are less at the Lithuanian coastline favourable for seaweed thickets to form (e.g. in the proximity of sandy fields), the key elements of the reefs are dense mussel colonies. In Lithuanian coastal waters, the density of mussels in such colonies may reach tens of thousands individuals Šventoji per square metre, their weight reaching 3‑7 kg. The available data suggest that the larger the number of colony-forming molluscs, i.e., the higher the density of these colonies, the more species of other benthic animals are observed there. For example, in small colonies with the mussel densities reaching only 5 thousand individuals per square metre, on average 8 other species of benthic animals are found, whereas with the mussel densities increasing to 15 thousand individuals per square metre, the average count of other animal species increases to 12. It was also established that in these colonies the molluscs settled on the top of the reef are four times bigger than the ones on the slopes. So far there is no clear scientific explanation to this phenomenon, although some scholars think that living on the reef tops offers mussels better conditions for filter-feeding and thus facilitates their growth.

Palanga Underwater ridges stretching into the sea away from the Palanga pier

The contour of a reef lying at the depths of 15-20 m in front of the town of Palanga

Reef crests Troughs between reef crests

68 THE BOOK OF THE SEA 69 Reefs Abundance of long-tailed ducks based on visual counts from Numbers of round gobies caught in Lithuanian territorial Black carrageen have the greatest biodiversity in the central part of the Baltic the shore (in thousands of individuals) waters by monitoring nets (number of specimens) (Furcellaria lumbricalis (Hudson), J.V.Lamouroux, 1813) Sea. During the spawning of the Baltic herring in April-May, their eggs deposited on the carrageen thalli attract numerous In the Lithuanian coastal waters between Palanga and other fish and sea birds. Šventoji, the black carrageen forms extensive zones of dense Annual growth rate of Furcellaria lumbricalis is about 3500 1392 meadows attached to different substrates of the underwater 1 cm, ant the thalli may reach up to 30 cm. During the 671 slope, such as gravel, cobble or boulders. The black carra- growth, its laminae branch into two (this is called dichoto- geen can itself serve as a substrate to other prevailing fauna mous branching), which means that this seaweed does not 107 80 72 and flora species, therefore the boulder fields with Furcel- have a single well expressed stipe. Black carrageen contains 18 laria lumbricalis meadows are distinguished as one of the some anti-bacterial, fungicidal and phytotoxic substances. 1438 Lithuanian coastal biotopes. This biotope is favourable to One of them is histamine. This substance is involved in all 1262 1354 2 other species of aquatic vegetation, while the majority of development stages of the seaweed providing defence against 886 537 fauna consists of mussels and barnacles. The meadows of grazing animal species. 434 Furcellaria lumbricalis are the main spawning grounds of 2006 2007 2008 2009 2010 2011 2012 2006 2007 2008 2009 2010 2011 2012 the Baltic herrings which reproduce in spring. The fry finds Green branched weed shelter from predators in their tangles and also plenty of (Cladophora sp., Kützing, 1843) Since the invasion of the round goby into Lithuanian waters in 2002, the num- food. Reef habitats based on the black carrageen meadows bers of mussels have significantly declined, leading to the changes of coastal reefs. Cladophora is a genus of green algae found in shallow lakes, In the places where the boulders used to be covered in dense colonies of these bi- rivers and seas, attached to boulders or submerged wooden valves, nowadays the bay barnacle prevails. Large mussels are found only on the top- constructions. Some 300 species of this genus are known most parts of the boulders; they are too large for gobies to swallow, and swimming worldwide, but only 2 species are common in the Baltic Sea: up to the top also requires much more effort. As mussels declined, velvet scoters Cladophora glomerata and Cladophora rupestris. Green also abandoned these sites where they used to forage throughout winter. branched weeds produce dense, tangled, branching, seg- Contrary to the coastal reefs, the offshore reefs retained abundant mussel col- mented strands of up to 13 cm long. onies. This makes them especially valuable feeding grounds for demersal fish, first Cladophora species are found at the depths of up to of all flatfish and cods, as well as for wintering waterfowl, such as long-tailed ducks. 10 m. The fastest growth rate is registered in May-June, so For instance, the reefs of Klaipėda–Ventspils Plateau located near the Latvian border by July, they may cover entire surfaces of certain boulders. at the depths of 24-40 m remain very important for both fish and birds. The concen- Cladophora cannot firmly attach to the substrates, therefore tration of long-tailed ducks over the reef is 5 times higher than in the surrounding they are sensitive to waves, which can tear them away and waters, while the density of cods and flatfish among the boulders of the reef is 2-3 carry floating in the water column or wash ashore where times higher than in the deeper areas. they decompose. Cladophora are capable of both sexual and asexual reproduction.

70 THEJŪROS BOOK KNYG OFA THE SEA 71 Reefs as early as 19th century attached to boats or in the ballast floating larvae that are carried away by currents as plankton. water. The first discovery of Amphibalanus improvisus was After a certain growth period which may last up to six moths, registered there in 1844 near the current town of Kalinin- they stop their floating journey and attach to a hard substrate grad. Nowadays bay barnacles are found in all parts of the transforming into adult barnacles. Their life span is 1‑2 years. Baltic Sea. Being able to adapt to changing temperatures and Barnacles live upside down, because they attach to vari- salinity levels, capable to survive in low-oxygen environ- ous hard surfaces by their head parts. The suitable substrates ments, under intense eutrophication and chemical pollution, include coastal rocks, shells of molluscs and turtles, hard barnacles are found at almost any coastline world-wide. skin of whales, crabs, underwater constructions and ship Amphibalanus improvisus forms a white or yellow cone- hulls. In order to protect ship hulls from damage that could shaped shell consisting of lime plates, which is usually 1 cm be caused by barnacle overgrowth, they are painted with tall and 1-2 cm wide. The abdomen is rudimentary and the special toxic paints damaging the entire aquatic ecosystem. thorax bears six pairs of dichotomous filtering limbs. As The alternative, environmentally friendly protection method– the upper plates are opened, bay barnacle protrudes these mechanical cleaning by lifting ships out of water–is much limbs outside to produce a fan-like structure. By periodically more expensive. The algae of the Cladophora genus are used in aquar- unfolding and retracting that fan, barnacles filter out from In addition to the shipping industry, barnacles cause therefore their numbers in such colonies are several times iums, where their tangles produce oxygen and purify water. the water tiny organic particles, other small animals and damage to underwater pipelines and other constructions, higher than those on plain boulders not covered by mussels. In some Asian countries certain Cladophora species are also phytoplankton cells, which all comprise their diet. and a lot of money is being spent to clean them from these Mussels have been cultivated in Europe for 800 years al- known under the name “Mekong weed” and are consumed Amphibalanus improvisus is a hermaphrodite (an or- crustaceans. The only predator of bay barnacle in our wa- ready and consumed by humans for over 20 thousand years. for food in fresh or dried form. In the Baltic Sea, green ganism producing both male and female sex cells), however, ters is the round goby. Some of the ancient coastal settlements were discovered by branched weeds are eaten by some invertebrates. cross-fertilisation is obligatory. From the fertilised eggs hatch archaeologists because of the remains of mussel shells left by Mussels the local dwellers. Bay barnacle (Mytilus sp., Linnaeus, 1758) Although in “typical” seas mussels reach 11 cm, in the (Amphibalanus improvisus, Darwin, 1854) central part of the Baltic Sea they do not exceed 3.5 cm, For a long time, scientists had been thinking that only one presumably because of the low water salinity (7–8 ‰). Low Barnacles comprise some 1 200 species world-wide, but only species, the blue mussel (Mytilus edulis, Linnaeus, 1758), had salinity also restricts the lifespan of mussels in the Baltic Sea. one of them lives in the Baltic Sea–Amphibalanus improvisus. lived in Lithuanian coastal waters, but the recent genetic There it lasts 12‑14 years, while in the more salty seas, some Despite their appearance, bay barnacles are crustaceans and analysis revealed that along with Mytilus edulis, the more specimens may reach up to 24 years of age. not molluscs. Their “cousins” are such familiar creatures as northern species Mytilus trossulus, as well as hybrids of both Mussels feed by filtering water and capturing organic crabs and lobsters. species were present. particles in their gills. To survive, some larger individuals Barnacles are considered to be among the most sed- Mussel colonies, wherein their weight may reach might filter up to 65 l of water per day–those attempting to entary marine organisms, however, the bay barnacle has 8–10 kg per square metre, provide exceptional hiding, feed- keep them in aquariums should ensure good circulation and arrived into the Baltic Sea from North American coasts ing and attachment conditions for other benthic animals, the largest possible volume of water.

72 THE BOOK OF THE SEA 73 Reefs A mussel colony Mussels of the Baltic Sea lead different lifestyles: in the therefore it prefers boulder fields with rich benthic flora southern parts of the sea they live on sandy substrates, pro- where it can find shelter. ducing entire colonies at the sites where they find anything to Rockpool prawns can reach more than 6.3 cm, their attach to. At the Lithuanian coasts, in the central Baltic Sea, transparent carapace is covered in orange or yellow spots and mussels live exclusively on boulders and other hard substrates dark brown stripes, while the front legs and and abdomen fea- attached by the so-called byssus strands. These strands are ture blue and yellow stripes. The colour intensity depends on based on the protein collagen, which also adds elasticity to our the living environment, the specimens living in murky waters skin. Byssus strands are both strong and very elastic. Scientists are much paler or might lack colouration altogether. are working to create a natural glue based on their chemical During the warm season the female rockpool prawns car- composition that could be applied in ocular surgery. ry some 400‑500 eggs on their legs and breed twice a year. The spawning is triggered by sufficiently warm water temperatures. Rockpool prawn The development of eggs is determined by photoperiod–chang- (Palaemon elegans, Rathke, 1837) ing duration of daylight. Planktonic larvae called zoeas, that hatch from these eggs, spend all summer drifting in the water The rockpool prawn is a species of the European coastal column. By autumn, juvenile prawns descend to the bottom to waters of the Atlantic Ocean, North and Mediterranean continue their life as adults. Palaemon elegans is preyed upon by Seas, which spread into the Baltic Sea in the 20th century. many species of birds, seals and predatory fish. The ever spread- How exactly this prawn became widespread in our sea is not ing Baltic population of Palaemon elegans raises great concern completely clear, but in some other territories of the former about possible displacement of the local species, the brown Soviet Union it was introduced intentionally. The species is shrimp, from its distribution range. So far, there is no scientific used for food in the Black Sea area. information on the ways these two species compete. In Lithuanian coastal waters, Palaemon elegans is most often found near the Palanga pier, Klaipėda mole and at Baltic isopod Karklė. The rockpool prawn does not burrow into sand, (Idotea balthica, Pallas, 1772)

This isopod species is a cosmopolitan widespread in Europe along the entire Norwegian coastline, in the Mediterranean and Black Seas, and even at the Atlantic coasts. In other seas, Idotea balthica is mostly found in the intertidal zone, while at the Lithuanian coasts it inhabits shallow parts of the underwater slope with abundant bottom vegetation on which it feeds.

74 THE BOOK OF THE SEA 75 Reefs although identification of sex is possible only after they valuable commercial fishes. Unfortunately, their stocks Eel is a predatory demersal fish. They usually spent reach lengths of 6‑7 mm. are being rapidly depleted–within the last 30 years, the the day hiding passively, for instance among aquatic These creatures can sometimes be found washed ashore stock recovery rates have declined by up to 100 times. In vegetation, stones or burrowed into a soft substrate, while together with the tangles of black carrageens and green Lithuania, most eels are caught by fish traps in the Curo- at night they leave their hideouts for active hunting. Adult branched weeds. nian Lagoon and in smaller rivers during migration. This eels forage on fish, frogs, crustaceans, and large insect lar- fish is an important object of recreational fishing, however, vae. The juveniles feed on small larvae and various worms European eel catching an eel with a fishing rod is quite a challenge. In that they find on the bottom. Mature eels migrating to (Anguilla anguilla, Linnaeus, 1758) Lithuania, eels are served smoked or marinated, or used to their spawning grounds cease foraging. Their intestines Although some 30 species of the genus Idotea are known cook a tasty fish soup. are thought to undergo complete resorption during mi- world-wide, only three of them are found in the Baltic Sea, European eels are distributed in Europe, North Africa and The life cycle of European eel starts and ends far away gration. and their appearance is very similar. All the three species part of Asia where they live in coastal waters, estuaries, from Lithuanian shores. Although nobody has ever observed arrived from the Atlantic Ocean when Baltic Ice Lake gained lakes and rivers. Eel’s body is long, thin, rounded and looks eels spawning in natural environment, based on the smallest Atlantic cod connection with the ocean. somewhat snake-like. The upper side is usually dark green, size of captured larvae the conclusion was made that their (Gadus morhua, Linnaeus, 1758) The males grow up to 4 cm and are larger than the the lower–yellowish, however, the colours change as the fish spawning grounds must be in the Sargasso Sea. The hatched females. The exoskeleton is yellow, brown or green with tiny matures, the dorsal side becoming dark blue or almost black, larvae migrate with the Gulf Stream towards European A cod is a desirable catch of any recreational fisherman. white dots, the females are usually darker. Idotea balthica can while the abdominal–silvery. Although eel’s mouth is not shores where they undergo metamorphosis and turn into According to the official data, the largest cod caught in be distinguished from other crustaceans by its flat tail plate very wide, it is full of small teeth designed to hold the prey. transparent little fishes devoid of pigmentation but already Lithuania weighed full 19 kg! Moreover, in Norway which with a tridentate posterior border, where the median process The European eel is one of the most mysterious fishes, resembling an adult eel. Upon getting pigmentation, young is further to the north than Lithuania and is notorious for is longer and acute. and for many centuries even scientists around the world did eels settle in various coastal waters or migrate upstream into its record-breaking fish, the largest captured cod weighted Idotea balthica is an omnivorous animal, feeding on not know where they reproduced and how they appeared freshwater bodies. As they reach maturity, the grown-up eels over 47 kg and was registered as an absolute world record– benthic micro- and filamentous algae, small invertebrates in our water bodies. Aristotle had been thinking that eels start the last journey of their lives back to the Sargasso Sea the largest cod caught by recreational fishing gear. and detritus. This is the key “herbivore” of the Baltic Sea, were emerging from mud, later this theory was replaced by where they are thought to spawn once in their lifetime and Nowadays the Atlantic cod is a very important com- although it does not ignore animal food either. The isopod another, stipulating that eelpout was the mother of eels. This to die afterwards. mercial fish of the Baltic Sea, and its stocks are strongly is a very important component of the aquatic communities theory must have inspired the German vernacular name of affected by intense commercial fishing. Although lately cod because it supports fish diversity, serving food to some 23 eelpout, Aalmutter, which literally means “the mother of eels”. stocks have been gradually recovering, the status of the species. Nowadays the species has been much better studied, and yet species is still classified as vulnerable. The main method of Isopods are among the most popular invertebrates used many questions about biology and ecology of eels remain commercial cod fishing is offshore bottom trawling. Fish- in scientific research. This popularity is due to the fact that unanswered. ermen who fish in the coastal waters mostly catch cods by their generations change in about half a year, and they do The seaside dwellers of the Baltic Sea were familiar using gill nets. Another fishing method popular in the past, not require any special care or conditions. What is rather with eels very long ago–according to archaeological data, by longlines, is seldom used nowadays. As for the receipts unusual among benthic invertebrates is that the females the inhabitants of the coastal areas used to fish and eat eels of cod preparation, there are very many of them. It is worth produce young which already resemble adult specimens, at around 6 000 B.C. European eels are among the most noting that salted or dried cods used to be one of the key

76 THE BOOK OF THE SEA 77 Reefs then use a special “dance” to attract females to them and Shorthorn sculpin guard the eggs laid in the nest till they hatch. Their lifespan (Myoxocephalus scorpius, Linnaeus, 1758) is 3‑4 years and the maximum body length reaches 11 cm. The three-spined sticklebacks inhabit both salty and The shorthorn sculpin is a fish of impressive appearance fresh water bodies: seas, estuaries and lakes. They are wide- widespread in all seas of Northern Europe. The fish is up to spread in the Northern Hemisphere, from the temperate 30 cm long, very spiky, usually dark in colour with a bright zone in Europe to the Black Sea, North Africa, but also in orange or red belly mottled with white spots. The head is North America, Greenland and East Asia. enormously big, with a broad forehead, equipped with large Sticklebacks feed on crustaceans, insect larvae and eggs spines. The eyes and the mouth are also very large. The of other fish. They are abundant in the Baltic Sea; at certain mouth is full of small teeth designed to grab and hold the locations, where they gather into shoals, they might even prey. eliminate zooplankton and thus provoke algal blooms. Sculpin is a typical demersal predator, ambushing its Sticklebacks use to be fished and used as fodder for prey from different hideouts at the bottom. Its diet consists provisions during long sea voyages, when the European numbers of small sharp teeth. The lower jaw has a long bar- ducks, pigs, farmed fur-bearing animals or other fish, and predominantly of other juvenile fish (cod, flatfish, European seamen sailed to discover distant lands. bel. The body is greenish with the shade of grey or brow and also used in fish oil production. Although never considered smelt, Baltic herring, etc.) as well as of small adult fish (sprat The success of cod reproduction highly depends on wa- mottled with brown spots. a valuable commercial fish, the three-spined stickleback has and sticklebacks) and larger crustaceans. ter salinity. At least 10 ‰ salinity and sufficient oxygen levels Cods are widespread in the North Atlantic and Arctic become a true “superstar” of laboratories due to its mor- Sculpins are of no commercial value, so they are not are necessary for normal development of cod eggs, therefore waters. Beyond doubt, this is one of the most important phological diversity, unique behaviour and short life-cycle, subject to specialised fishing, however, recreational fisher- they spawn at deeper depressions, sometimes up to 100 m. marine fish species of the Baltic Sea where it is adapted to which make it an irreplaceable test animal in evolutionary men catch them quite often when using animal bates. Taken below the surface. Cod fecundity is known to depend on the low salinity conditions. biology or behavioural studies, the numbers or studies being out of the water, this fish demonstrates a peculiar behaviour: their size, and the biggest females were reported to produce comparable to those done on mice or Drosophila fruit flies. it puffs up, spreads its spikes in defence and produces a buzz- up to 4 million eggs. Three-spined stickleback From their feeding grounds in the Baltic Sea, stickle- ing sound by vibrating some muscles in the frontal part of its The Atlantic cod is one of the main predators of the Bal- (Gasterosteus aculeatus, Linnaeus, 1758) backs migrate for spawning to the coastal waters including body. tic Sea mainly feeding on other fish, such as Baltic herrings the Curonian Lagoon. The eggs are released in batches in Shorthorn sculpins spawn in the coldest season–in and sprats, and they also demonstrate some cannibalism An outstanding feature of this species is three spines at the May-July, when the water warms up to 18‑20 °C. December‑February. The females, who are normally slightly when larger cods prey upon their smaller kin. Large crusta- dorsal fin providing defence against predators as well as larger than the males, produce up to 2 700 red sticky eggs, ceans, such as Saduria entomon, also supplement their diet. bony plates on the flanks producing a sharp edge. The dorsal which clump into clusters and stick to seaweeds. The males This species actively hunt for their prey in the demersal and part is greyish-green, the sides are yellow or silvery. Before protect and defend these eggs. pelagic zones of the water column. spawning, the males turn red and the females develop dark These fishes are usually found in the coastal waters up to Juvenile cods feed on various crustaceans and worms. spots on their sides. 25 m deep although sometimes they are caught also at greater The body of cod is spindle-shaped, with a large head. The males demonstrate interesting behaviour: they build depths. They are sedentary but demonstrate some seasonal The mouth is extremely large and equipped with great nests on the bottom, using plant material and their mucus, relocations, moving close to the shore in summer and deeper

78 THE BOOK OF THE SEA 79 Reefs The lumpfish spends most of its life far away from the shores, in the open sea up to 200 m deep, hiding among boulders and rocks on the seabed and approaching the shores only during its reproductive migrations. Several catches of lumpfish have been registered even in the northern part of the Curonian Lagoon during the spawning period. The spawning of lumpfish is extended in time and lasts from February till May. The eggs are released in batches on in winter. Sculpins occupy different habitats, both on sandy hard stony substrate or in the thickets of seaweeds (such as and rocky bottoms, while temperature or salinity changes kelp). The females leave the eggs after spawning and retreat have little effect on their spacial distribution. from the shores, while the males stay to take care of the eggs, which they fan with their pectoral fins. The hatchlings are Lumpfish also supervised by the male for some time, and only later, as (Cyclopterus lumpus, Linnaeus, 1758) they gain in size, they start independent life. In Lithuania, this fish has no commercial value and is The lumpfish, whose vernacular Lithuanian name translates not subject to targeted fishing or used for food, however as “the sea toad”, is an odd-looking Baltic fish, growing up to in Iceland and Denmark, it is consumed salted, dried or 5.5 kg, although in Lithuanian waters much smaller individ- smoked. uals under 200 g are caught only occasionally. The natural distribution range of this species covers the northern part of Eelpout the Atlantic, the North and Baltic Seas. Lumpfish is a relict of (Zoarces viviparus, Linnaeus, 1758) the last glacial period (12 000 year ago) in the Baltic Sea. The diet of this demersal fish mostly consists of crus- The eelpout (also known as viviparous blenny/eelpout) be- taceans, bristle worms, fish larvae and small fish. The most longs to the marine fish family Zoarcidae. From appearance, Lumpfish active foraging period is in winter, while during the spawn- it resembles an eel, however, the elongated body is usually ing it ceases feeding altogether. light yellowish with a pattern of dark spots. The eelpout body The body of lumpfish is short, almost spherical and de- is slimy, its small scale are sunk into the skin, leaving the im- void of scales. The upper side is dark, greenish or grey, while pression that the fish is scaleless. The largest specimens reach the lower side is usually pale yellow. The mouth is small, 50 cm in length and 500 g in weight. They are found in the adapted to small-sized prey. The pelvic fins have evolved into coastal waters of the seas of Northern and Eastern Europe. suction discs which it uses to attach to boulders. Among the Baltic fish, it is a true relict of the last glaciation.

80 THE BOOK OF THE SEA 81 Reefs This fish is peculiar because of its bones which are Freshwater fish greenish in colour due to the pigment vivianite. The green skeleton may appear a bit weird, however, the flesh is per- The Baltic Sea salinity is relatively low, therefore its coastal fectly edible. waters often contain some typical freshwater immigrants: The young of eelpout have a great similarity to the European perch, pike-perch, roach, freshwater bream, white glass eels, therefore for long years, before the true breeding bream, etc. However, their abundance in the coastal waters biology of the European eel was discovered, the eelpout was depends on the season and hydrological conditions–these broadly believed to give birth to eels. fishes are usually observed there in the warm season and The eelpout fully justifies its vernacular names–contrary calm seas. Pike-perch to most other familiar fish species, it does not spawn eggs, Freshwater fish are usually absent from the offshore giving birth to 30‑400 fully developed young instead. This waters of the Baltic Sea, but at the coastal waters, especially fish is characterised by internal insemination and complete in the warm season, they constitute a significant share of development of eggs and hatchlings in the mother’s body. commercial catches. The dominant freshwater species in The eelpout is a demersal fish usually found at depths of those catches are the European perch, pike-perch and fresh- up to 40 m on solid stony or rocky bottoms, where it hides water bream. in cracks or among bottom vegetation. It is passive in day- Some freshwater species, such as perches and Roach time, foraging more actively at night. The main diet consists pike-perches, migrate from the Curonian Lagoon to the of snails, crustaceans, bottom-dwelling worms, fish fry and Baltic coastal waters each spring after spawning, move eggs. They themselves fall prey to many predatory fish and between brackish and freshwater zones in the summer and fish-feeding birds. in autumn, when the sea water gets colder, they return to the Curonian Lagoon for wintering. This migratory behaviour is considered to be linked with better foraging conditions in Freshwater bream the Baltic Sea and a positive impact of the brackish water on physiological processes of fish. It may also be the case, that migrations allow these fishes to get rid of some ectoparasites that do not tolerate brackish water. Freshwater fish species usually swim into Lithuanian Baltic coastal waters from the River Šventoji and the Curoni- an Lagoon. Most freshwater fish do not breed in saline water and start their migrations to the sea only after spawning in fresh waters. Their abundance and species composition in the marine coastal zone is directly linked with the state of European perch

82 THE BOOK OF THE SEA 83 Reefs fish communities in freshwater bodies, and the latter often The intensive spawning of round gobies lasts from depends on fishing intensity and eutrophication. April to June in batches and in several rounds. The eggs are With the approach of autumn, in September‑October, attached to stones, plants and other substrates. The males numbers of freshwater fish at the sea coast diminish, but guard the eggs from predators and fan them with their fins. they are replaced by migratory anadromous fish swimming Many males die after the breeding season. to spawn from the sea into the rivers, such as vimba bream, The diet of round gobies is pretty diverse, however, the Atlantic salmon, sea trout and European smelt. True marine major part of it consists of various molluscs, crustaceans, species, such as cod, Baltic herring or flounder arrive in the other invertebrates and small fish. coastal waters in larger numbers only as the water gets cold. With their numbers growing steadily, gobies tend to So in the course of a year, the coastal waters are frequently become the main catch of the recreational fishers, fishing in predominated by freshwater fish in the warm season, by the Baltic coastal zone. Their share in commercial catches is marine species in the cold season, while in autumn they are also increasing. Although this fish is not large it can be used filled with migratory fish species. for food–fried, smoked or canned. They are considered to be one of the most numerous Round goby fish species of the coastal waters at present, while in future (Neogobius melanostomus, Pallas, 1814) their abundance is likely to decline. This is a usual popu- or habitats. It cannot be completely rejected that this small individuals were registered, till 1997, when the wintering lation trend of all invasive species–as they occur in a new fish may even influence the abundance of marine waterfowl– stock reached 2 000 birds. Then, a rapid decline of the The round goby is a species provoking heated discussions environment with no natural enemies, diseases, competitors the abundant populations of gobies might be consuming numbers of wintering eiders followed, and a decade later and arguments like no other fish. In the Baltic Sea, it is and other regulatory factors, the population explodes, but large quantities of molluscs which are an important food only 100 individuals were counted in Lithuanian waters. In found in coastal waters and freshwater estuaries. The natural eventually a decline follows till the population is stabilised. source to certain birds, thus causing a shortage of food and the last few years only individual birds have been spotted distribution range of round goby covers the Pontic–Caspian The round goby is considered to be an especially aggres- pushing them away into different areas. On the other hand, at the Lithuanian coasts, and in some years no observa- region (encompassing the basins of the Black, Azov and sive invader capable to produce a profound impact on the fish-feeding birds, such as cormorants, must be undoubtedly tions were registered altogether. Caspian Seas), while in Lithuanian waters the first specimen ecosystem. Spreading rapidly, round goby is likely to com- happy about its arrival. The Steller’s eider is a benthic feeder, foraging on was caught in 2002. pete with local fish species (flounder, eelpout, etc.) for food bottom molluscs and other invertebrates. At the Lithuani- The fish is relatively small, its body short and sturdy, the Steller’s eider an coastline, it used to be very attached to their traditional head is big, mouth sufficiently wide, equipped with small (Polysticta stelleri, Pallas, 1769) wintering grounds over the mosaic cobble seabed between frontal teeth and another set of teeth deeper in its throat spe- Karklė in the south and Kunigiškiai in the north. The win- cialised for crushing molluscs. The body colour is adapted to This is one of the rarest sea ducks. It is included in the IUCN tering flocks are usually very dense, and all the birds dive its surroundings, however, the prevailing colouration is dark, globally threatened species list as a vulnerable species, and in highly synchronised manner. almost black. The dorsal fin has a clear black spot in a yellow is also listed in the Lithuanian Red Data Book. The num- The Lithuanian wintering grounds near Palanga used frame, while the ventral fins are conjoined. bers of wintering Steller’s eiders counted at the Lithuanian to be the southernmost aggregation of this species. Larger coasts had been gradually increasing from 1969, when 10 aggregations are registered at the Saaremaa Island in

84 THE BOOK OF THE SEA 85 Reefs Estonia, but even there their abundance has been declining lately. One possible explanation to this decline of the Steller’s The water column eider in its Baltic wintering grounds is a shift in wintering locations linked with the global warming: more and more birds tend to stay for winter in the northern seas, near the Kola Peninsula and in northern parts of Norway, instead of flying to the Baltic Sea.

Long-tailed duck (Clangula hyemalis, Linnaeus, 1758) In this environment, everything and everyone is in This is a northern species breeding in small tundra lakes, at the used to include a few thousand, or even over ten thousand motion. What differ are the speeds and directions. shores of the northern seas and sometimes also in larger lakes. birds. However, in the last years, these wintering flocks have The nest is usually built on the ground in proximity to water. dramatically diminished. The most likely explanation of this Some move at will, some helplessly drift carried by Within the last two decades, the North-European/ rapid decline is the negative impact of an invasive species, West-Siberian population of the long-tailed duck had shrunk the round goby, on the availability of mussels, the favourite waves and currents. This is the offshore realm, home by almost three times–from 4.6 to 1.6 million birds. In 2012, food of these ducks. It is interesting to note, that the abun- the species was included into the list of globally threatened dance of long-tailed ducks wintering in front of the Curo- to both close relatives of whales and the smallest species. Accidental catches by fishing gear, oil pollution, eu- nian Spit and foraging mostly on benthic crustaceans has trophication and effects of the global warming were identi- changed insignificantly. inhabitants almost invisible to a naked eye. This is fied as the key factors affecting their population. According to its feeding habits, the long-tailed duck The Baltic Sea is a wintering ground of some 90 % of is a benthic feeder, foraging on demersal invertebrates, the world where no one stays in one place for too the regional population of the long-tailed duck. The birds molluscs, sometimes also fish eggs. The diet may differ in arrive in the Baltic Sea after moulting in Northern Russia in different habitats and parts of their range. At the Lithu- long, nonetheless, it has its own rules and order. October‑November and stay till April‑May. anian coasts, their main food near Palanga are mussels, Merely a few years ago, they were abundant at the while along the Curonian Spite–the isopod Saduria Lithuanian coasts near Palanga, where the wintering flocks entomon.

86 THE BOOK OF THE SEA 87 The water column 88 THE BOOK OF THE SEA 89 The water column Seas and oceans contain about 98 % of the total water resources on Earth. The average thickness of the global water layer is 3 680 km, and this water column is referred to as the pelagic zone (originating from the Greek word pelagos meaning B “open sea”). The deepest layer of the water column on Earth is almost 11 km, while in the Baltic Sea it is way more modest–the deepest depression is the Landsort A Deep but it reaches only 459 m. The average water column of the Baltic Sea is about 53 m deep. This zone is full of marine life, majority of which consists of microscopic algae or animals almost invisible to a naked eye (they are called phytoplankton and D zooplankton). They constitute about half of all the diversity of living organisms in the Baltic Sea. However, this realm is also home to the largest animals, the marine

C F E mammals. Three species of seals and the only cetacean species in the Baltic Sea, the harbour porpoise, are the rulers of the pelagic zone who do not have natural enemies superior to them in their environment. Even so, they still balance on the brink of extinction because of human activities. The water column is a world where everything and everyone is in motion, because there is nothing to attach to. The only difference is that some, such as fish or A Baltic grey seal D A school of sprats marine mammals, can swim actively and reach the places they want at will, while B Common murre E Opossum shrimps some others have simply adapted to survive drifting with the currents or being C Atlantic salmon F Common jellyfish tossed by turbulence. Despite constant water circulation in the water column, it retains distinctive layers that are important to many marine organisms. The surface layer of the Baltic Sea up to 10-20 m deep warms up in summer and does not mix with the deeper layers. It may get as warm as 16–20 °C, while the temperatures beneath reach merely 4–5 °C. This layer usually has enough light, therefore its warmer waters facilitate the most intense growth of microscopic algae. However there are animals, such as cod, that carefully avoid higher temperatures typical to this layer. The intermediary water stratum where the temperature gradient is steep is called the thermocline. This layer is below the warm surface layer and seldom exceeds 10 m. Only in calm weather with steady continental winds, which push the surface waters further offshore in the course of a few days, the cold but clear deep water rises up to the shore. Such stratification of the upper layers of the water column is common only in summer, because the autumn storms stir these strata up, and the temperatures in the water column even up till the next summer.

90 THE BOOK OF THE SEA 91 The wwaatterer col columnumn Commercial catches of the European whitefish Commercial catches of the twaite shad Phytoplankton can be transported long distances in the water column, and in the Curonian Lagoon (tonnes) in the Curonian Lagoon (tonnes) since nutrients dissolved in the water are available every- Phytoplankton consists of microscopic algae, and their where, this “migratory” lifestyle causes them no problems 60 300 generalised name originates from the Greek word planktos, leaving only one concern–to stay in the upper layers of the meaning errant or drifting with the current. The largest phy- water column, where there is enough light. In order to get toplankton organisms may reach the size of about a quarter more nutrients from their environment, the cells develop to 40 200 of a millimetre, while the smallest are less than a micrometre, produce the largest possible surface area through which they i.e., they measure in thousandth parts of a millimetre. These are absorbed. When both nutrients and light are abundant, organisms are sampled by very dense nets, although the col- and the environment stays warm and calm, some species of 20 100 onies of phytoplankton that dye large areas of the sea surface phytoplankton multiply very rapidly. Their colonies dye water can be observed even from satellites. surface in bright colours. In the Baltic Sea, the colour usually Just as the grass and the trees on the dry land, phyto- is green–this phenomenon is called an “algal bloom”. 0 0 plankton are the main “green” products of the sea, serving How come that the cells of phytoplankton, which are

1945 1955 1965 1975 1985 1995 2005 2015 1945 1955 1965 1975 1985 1995 2005 2015 food to other organisms, first of all to small animals inhabiting slightly heavier than water and gradually sink, manage the water column–zooplankton. The growth of phytoplankton to stay afloat for so long? The sinking is slowed down by Contrary to the temperature stratification, vertical stratification of salinity is depends on the available light and dissolved nutrients. On various adaptations, such as different projections, spikes caused by the fact that the deeper, cooler and saltier water has higher density and land, plants get nutrients via their root systems, but the phy- and other forms designed to increase cell surface but not its is heavier. In the central part of the Baltic Sea bordering Lithuania, the surface water toplankton cells absorb them directly from the surrounding volume, or tiny locomotive flagella and bristles, enhancing salinity of about 7 ‰ remains more or less stable down to the depths of 60 m, then medium. The absence of roots means that phytoplankton cells the ability to stay “suspended” in the water. Cells might also within the next stratum of about 20 m it rapidly increases to 10–11 ‰, after which the salinity changes very little, no matter how deep. This steep salinity gradient, which in the southern part of the sea starts even at lower depths of some 40 m, is called the halocline. This layer is especially important to the deepwater species preferring cold water, some of which have survived since the last glaciation. This stratum is important because it creates a rather strong barrier preventing the deep water strata from mixing with the surface layer. Because of it, the oxygen content below the halocline is usually lower, and the stagnant water of the deep takes a decade to be completely refreshed. This gradual replacement is caused by the inflow of heavy and saline water from the Norths Sea, usually caused by the winds. It reaches different parts of the Bal- tic Sea at a different pace–the stronger the winds, the further north this water flows. In those periods the “old” water from the depths rich in different accumulated materi- als is pushed out into more shallow areas.

92 THEJŪROS BOOK KNYG OFA THE SEA 93 The water column Zooplankton have various “buoys“ inside–the vacuoles filled with low scientists who study them usually dive in the water column in density liquids, and some species can connect their cells to remote offshore areas where the seabed is too deep to see. produce chain-like colonies. Up to 1 200 species of zooplankton have been regis- Just as trees on the dry land, phytoplankton perform the tered in the Baltic Sea. This number does not include large process of photosynthesis and produce oxygen necessary for numbers of small pelagic larvae of those animals whose other aquatic organisms to breath. Phytoplankton do not need adult forms are sessile and live on the bottom. The numbers leaves, photosynthesis takes place in chloroplasts contained in of these larvae of bivalve molluscs and other benthic animals their cells. Moreover, by performing photosynthesis, phyto- may reach thousands per cubic metre of water. Transported plankton not only replenish oxygen content in the water but by currents, the organisms at that stage of their development also reduce the amount of carbon dioxide in the atmosphere are able to reach territories that adult individuals would by accumulating carbon in their cells, which is eventually never be able to get to. transferred to other organisms in the food chain as phyto- Zooplankton comprise an important part of aquatic plankton get consumed by them. If that does not happen, the food webs; small zooplankton usually feed on phytoplank- cells eventually die and sink to the bottom, being decomposed ton, while they themselves are consumed by larger forms of by bacteria along the way or accumulating on the seabed as zooplankton or larger marine inhabitants, first of all fish. It dead organic material. The latter either stays intact for long is interesting to note that krill, which is part of zooplank- periods of time or is consumed by the benthic animals. ton in the Antarctic waters, is the main food source of the largest marine mammals–whales. The key fish species of the Zooplankton Baltic Sea, the Baltic herring and the European sprat, feed exclusively on zooplankton, mostly on copepods. With the Zooplankton is a collective term denoting aquatic animals explosion of the sprat stocks, competition over food resourc- that spent all or most of their lifetimes in the water column. es has increased, the trend showing growing numbers of fish Some of them drift with the currents and are not capable of with their stomachs filled with ever smaller organisms. swimming actively, while others move actively at the speeds of up to 7‑8 m per minute or 1.5 km per day, migrating deeper Opossum shrimp during the daytime to hide from predators in the darkness (Neomysis integer, Leach, 1814) and resurfacing to feed at night. Zooplankton consist of either microscopic animals that are poor swimmers, or larger No wonder that these animals resemble shrimps–they are animals with soft body texture, such as jellyfishes. The largest also part of higher crustaceans (class Malacostraca) which of them are among the longest sea creatures reaching 40 m, encompasses some 25 000 species. Mysids, or opossum but these giants do not live in the Baltic Sea. In order to see shrimps, are slender free-swimming transparent crustaceans these soft-bodies animals or to collect their samples safely, the of about 17 mm. Their head, eyes and thorax are shielded by

94 THE BOOK OF THE SEA 95 The water column a well-developed carapace. The rostrum is acute but short. Opossum shrimps play a very important role in marine In early 20th century, the twaite shad was one of the These crustaceans also have two pairs of antennae the shapes food webs, sustaining fish stocks of commercial importance. most abundant and important fishes of the herring family in whereof are important identifiers of species. Some studies showed that during the cold season about the North and Baltic Sea basins. The catches were quite sig- Contrary to shrimps, mysids live in swarms that are 80 % of the diet of cods staying at the depths of 50 m con- nificant: in 1930s, Lithuanian fishermen would land 14‑60 t easy to spot to predatory pelagic fish during daytime. In sisted of mysids. annually. The stocks started to shrink in the first half of the the wild, swarming is a simple survival strategy that many 20th century in the entire range of their distribution. In organisms use, enhancing the chance of a particular indi- Twaite shad the post-war Lithuania, the catches were steadily declining, vidual to survive predator attacks. To avoid the attention (Alosa fallax, Lacepède, 1803) till from the end of 1950s they were no longer registered in of predators, mysid swarms descend into the darker depths usually found in estuaries and coastal waters, where they stay commercial catches. Then the twaite shad was enlisted in the during the day, while at night they return to the surface This is a fish of the herring family living in the Northeast At- for about a year. Shads tolerate oceanic salinity, the brack- Red Data Book of Lithuania. The prevailing opinion is that layers richer in food. In spite of that, mysids are an impor- lantic, from the southern coasts of Scandinavia to Morocco, ish Baltic Sea water and fresh water. They swim in schools the negative impact on shad stocks in the entire distribution tant food source to fish. including the British Isles and the Baltic Sea. From appear- migrating in the water column in the course of a day from range has been produced by climate change, construction of Mysids are known as “opossum shrimps”, because they ance, the twaite shad resembles the Atlantic herring, it may the surface to the demersal layers in pursue of their meals. dams, pollution and overfishing. In the middle of 1990s, the feature a brood pouch resembling the marsupium of opos- grow up to 60 cm and 1.5 kg. This species has a characteristic Twaite shads feed on juvenile fish of other species (Baltic population spawning in the Curonian Lagoon unexpectedly sums. Mysids carry their eggs in this “pocket”. An important dark spot behind its gill covers and a row of 6‑10 similar herring, sprat, etc.) and crustaceans. sprang back to life and became so abundant that the species reproductive factor is the ambient temperature which deter- spots placed along the flanks (although sometimes they are Twaite shads gather for spawning near estuaries and was withdrawn from the Red Data Book and even a limited mines how many generations will be raised per year. hardly visible or not visible at all). The body is covered in river deltas in March‑April, the males being in their 2nd commercial fishing was resumed. The twaite shad remains Neomysis integer easily adapt to changing salinity large thin scales. or 3rd and the females in their 3rd or 4th year. As the water a protected species under the EU Habitats Directive. Lately, levels, which allows them to spread broadly from the Baltic These fish tend to stay in schools and migrate long dis- warms up to 10–14 °C, they rush upstream into fresh waters, however, a new decline of stocks has been observed, the like- and North Seas down to the Mediterranean. They are also tances. They are most common in the offshore areas stretch- usually rising just a few kilometres, however, spawning as far ly cause being overfishing. When removed from the water, quite common in brackish bays and lagoons. ing along the sea or ocean coastline, while their juveniles are as 400 km upstream from the sea has also been registered. twaite shads start rotting very soon, so they require a special There is some evidence that in Lithuania individual shads processing and preparation for consumption. On the other used to swim upstream as far as the town of Prienai. Nowa- hand, the fish is delicious and fat, usually consumed smoked, days these migrations no longer happen, and the spawning marinated and sometimes salted. takes place in the Curonian Lagoon at the Nemunas delta. Spawning proceeds near the surface in May (hence a popular Baltic herring local name, translating as “the Mayfish”), usually at night, (Clupea harengus membras, Linnaeus, 1761) when water temperature reaches 12–22 °C. While spawning, shads produce a purring noise with their tales, which must The herring is a typical maritime species. In the Baltic Sea, have given them their Lithuanian name “perpelė“. They pro- the Atlantic herring is adapted to the low salinity and is duce some 12-15 (up to 230) thousand eggs which drift in the called the Baltic herring. Sometimes they even enter the water or sink to the bottom. The larvae hatch in 2‑8 days. Curonian Lagoon with a surge of the brackish water. In

96 THE BOOK OF THE SEA 97 The water column spring, large schools of herring migrate from their winter- fattened, possibly because of the competition with sprats ing and foraging grounds towards the spawning areas near which have become very abundant. the coast. Herrings are served fresh, pickled or smoked. The feeding habits of the Baltic herring change along with their growth: the juveniles feed on small crustaceans European sprat and zooplankton in the water column, while the adult fish (Sprattus sprattus balticus, Girgensohn, 1846) prefer larger bottom dwelling animals. Although herrings are a favourite food of many pred- European sprats, also known as brislings (German name: ators, such as predatory fish, sea birds and seals, they are Breitling, Latvian: Bretlina), live in the North-East Atlantic: well adapted and capable to escape predation: they swim in in the North Sea and surrounding waters–up to the Lofoten schools, blend well with the ambiance thanks to their silvery archipelago in the North, western part of the British Isles, grey colouration, have acute sense of hearing and demon- the Baltic Sea and down to Morocco in the South. They are Baltic herring strate very short reaction time to a danger. also found in the northern Mediterranean and the Black Sea. The dorsal part of herring is dark, the sides silvery and These typical marine fishes are also adapted to brackish wa- the body is compressed on the sides. The scales are small ter, therefore they are very abundant in the Baltic Sea. Sprats and thin. The Baltic herring is smaller than its relative the live in large schools in the surface layers of the water column Atlantic herring, reaching the size of up to 25 cm, and in up to the depths of 5-6 m. Sprats are extremely numerous in exceptional cases–up to 37.5 cm. The life span can be as long Lithuanian waters. as 10 years, but in most cases it is limited to 3-6 years. Both larvae and juvenile sprats, and the adults feed on Baltic herrings spawn over submarine banks, ridges and zooplankton, only the size of the prey depends on the size shallows covered in algal meadows in the coastal waters up of the fish at a particular stage of their lives. A recent study to 20 m deep when the water warms up to 10 °C. Majority of revealed that sprats also forage on eggs and hatchlings of cod, the population breeds in spring, a smaller part–in autumn. A thus being able to influence the reproduction success of the single female may produce up to 65 000 eggs. latter; even more so, because they also compete with the cod People dwelling at the coasts of the Baltic Sea used her- larvae and juveniles for limited supplies of zooplankton. On Sprat rings for food at least since 6 000 B.C. Nowadays, the Baltic the other hand, the cod is their main predator regulating the herring remains an important commercial fish. In the Baltic abundance of sprat. Sprats are also preyed upon by salmon, Sea they are fished with trawls and other nets, often in the sea trout, sea birds and other predators. coastal waters close to the spawning areas. The sprat is a small fish similar to an undersized Baltic Not long ago, the Baltic herring was the most numerous herring. They differ from the latter by their belly with fish species in the Baltic Sea, however, in the last few decades a strong keel of scutes. The dorsal part is dark greenish, their population has been shrinking and the fish appear less the sides are silvery. The scales are thin and easily shed.

98 THE BOOK OF THE SEA 99 The water column Sprats reach maturity within 1-4 years, as the body length In the Kaliningrad district of the Russian Federation, Euro- becomes 8–12 cm. The life span is up to 6 years, the maxi- pean whitefish have been bred artificially and released in the mum size is 18 cm. lagoon as the fry gets bigger for several years already. The major share of sprats caught in the Baltic Sea are The European whitefish has always been a desirable used to produce fodders for farmed fur-bearing animals or catch of local fishermen, intensively harvested by nets. fish powder. Another part of the catches is used for human Whitefishes can grow really big, up to 2-3 kg, although an consumption: salted, marinated or smoked. Marinated Euro- individual as big as 10 kg has also been officially registered. pean sprats are often sold under commercial name of “kilka” Before the World War II, the catches of whitefish in the (which actually applies to the Black and Caspian Sea sprat), many different habitats, both in freshwater bodies (lakes and Curonian Lagoon averaged over 40 t per season, sometimes big. In the sea, they usually stay in the brackish water areas while smoked and canned they are sold as “sprats” (although rivers) and in seas. The Baltic population of whitefish spawn peaking up to 100 t. Commercial catches in 1960-70s used close to river mouths. Vimba breams are migratory fish the Lithuanian name is bretlingis). The stocks are extremely either in the sea (the Gulf of Bothnia) or migrate into the riv- to reach 20-30 t, but then they shrunk to very small quanti- swimming to spawn from the sea into the rivers. In Lithua- rich, although certain decline has been registered after the ers. Our coastal waters are inhabited by the migratory form of ties. Presently, the status of the European whitefish stocks at nia, vimba breams inhabit the Curonian Lagoon and larger population peak in the middle of 1990s. the European whitefish, that lives in the demersal layers of the the Lithuanian coastal waters is critical, and only separate in- rivers, such as the Nemunas and the Neris. They tend to Sprats spawn in the deep parts of the Baltic Sea, for coastal waters but migrates for reproduction into the freshwa- dividuals are caught. Such a dramatic decline of this species stay in the coastal waters, usually up to 20 m deep. instance over the Bornholm, Gdansk or Gotland depressions, ter Curonian Lagoon. was caused by overfishing and, possibly, climate warming The hatchlings feed on plankton and stay in the rivers especially, over the seabed slopes, usually at the depths of Whitefish feed on benthic and planktonic crustaceans as along with the negative impact of eutrophication on the till the autumn, then set off for the sea. In the sea, vim- 50–60 m. They produce some 6 000–14 000 buoyant eggs, the well as other invertebrates. They themselves are a favourite spawning grounds located in the Curonian Lagoon. In spite ba breams forage on crustaceans, insect larvae, molluscs, larvae rise to the surface layers of the water column and the food not only to humans. It was established that the seals of of that, this fish does not enjoy a special protection status in shrimps, less often on aquatic vegetation. Juvenile vimba juvenile fish stays in the same areas or swim closer to coastal the Baltic Sea living at the Swedish coasts mostly feed on this Lithuania, except for a certain protection level offered under breams fall prey to predatory fish, water birds and other banks and shallows. The spawning period is prolonged, rang- particular fish. the EU Habitats Directive. aquatic predators. ing between March and August, but the peak is reached in Reproductive migration of mature whitefish (some in- European whitefish living in the sea accumulate in their The vimba bream belongs to the carp family (Cypri- April-May, when the surface layers start to warm up faster. dividuals reach reproductive age as early as in the 5th year of muscles a lot of fat necessary for long migrations, therefore nidae). Its dorsal part is bluish-grey, the flanks and belly their life) into the Curonian Lagoon via the Klaipėda Strait they are considered very valuable and delicious fish. are silvery. The scales are large. The body is medium deep, European whitefish starts in September, reaching its peak in October and early compressed on the sides. The mouth is inferior, capable of (Coregonus lavaretus, Linnaeus, 1758) November. Then in late November–early December, they Vimba bream protruding like a tube. The anal fin is very long. A distinc- concentrate at the shallow spawning grounds characterised (Vimba vimba, Linnaeus, 1758) tive edge devoid of scales stretches between the ventral and This is a fish of the salmonid family widespread from West by hard gravel substrate which are located at the western anal fins. The pectoral, ventral and anal fins are yellowish, Europe to Alaska and North America. The European white- coast of the lagoon between Nida and Šarkuva, as well as Vimba breams are widespread across the basins of the North, while the dorsal and caudal fins are grey. They reach 40- fish is easily recognisable among other fish by a small fleshy at the southern coast between the settlement of Šaksvytė Baltic, Azov, Black and Caspian Seas. In Lithuania, a land- 45 cm and 1.5 kg, very rarely up to 50 cm and 2 kg. Vimba adipose fin located on the dorsal part, between the dorsal and (Kashirskoje) and the mouth of the Deimena (Deyma) river. locked population was created after a dam was built on the breams grow slowly, and a ten year old fish usually weigh caudal fins. The sides are silvery, the upper jaw is protruding The spawning lasts till the freezing of the Curonian Lagoon Nemunas river to create the Kaunas Reservoir, and they 750‑850 g. and longer than the lower one. European whitefish live in in December. The productivity reaches 23 000‑100 000 eggs. successfully reproduce although the fish do not grow very

100 THE BOOK OF THE SEA 101 The water column The spawning takes place in May-June at the shoals and up to 30 cm or even longer. Their distinctive features with the start of the breeding migration (usually at the end rapids of the rivers, over gravel and pebble riverbeds, as the are an intense smell which resembles of cucumbers and of summer and in autumn) they approach the shores and water warms up to +13 °C or more. The males reach maturity a small adipose fin typical to their relatives, the salmon- migrate into the freshwater bodies to spawn. in their 5th, the females–in the 6th year. The eggs are released ide fish. Juvenile salmon are preyed upon by many predatory in batches. A single female can produce 48‑120 thousand eggs. The European smelt lives in seas, estuaries and deep fish, fish-feeding water birds (such as cormorants) and such During the spawning, vimba breams turn dark, with their dor- lakes, its distribution range covering the North Atlantic aquatic predators as otters. Adult salmon are too large for sal parts getting almost black, the fins gain a shade of red, and starting south of the White Sea and down to the western many predators, however, for seals in the sea they are a true the male bodies become covered in breeding tubercles. After coasts of France, including the Baltic Sea. delicacy. Juvenile salmon in rivers forage on various inver- the spawning, the fish return to the sea. People have been fishing smelts since long ago, for tebrates, such as aquatic insects, molluscs, and crustaceans, The vimba bream is a commercial fish in Lithuania. They instance some written sources of the 15th century mention Atlantic salmon and on other fish, while in the sea their diet consists of crus- are valuable and delicious. The best value is in autumn, when smelts as one of the most important fish species used for food (Salmo salar, Linnaeus, 1758) taceans, sandeels, sprat, Baltic herring and other fish. their flesh contains 12–13 % of fat. After the reproduction, the in the eastern part of the Baltic Sea. Nowadays these fish, The salmon, which is considered a royal marine fish, fat content shrinks to 2–4 %. Vimba breams are served fried, especially popular among Lithuanians, are consumed fried, The salmon is widespread in the temperate to polar latitudes has a fusiform (spindle-shaped) body with a relatively marinated or pickled. They are especially delicious when marinated, dried, smoked or prepared in other ways, and they of the Northern hemisphere. In the West Atlantic, salm- small head, its back is blue, the flanks are silvery and the smoked cold or hot. Historically, in Lithuania their arrival also serve as a popular bait for fishing predatory species. The on are found from West Greenland to Quebec in Canada belly is white. The caudal fin is truncated, the flanks feature used to be celebrated along the banks of the Nemunas river stocks are strong, although in some areas of the Baltic Sea and the Connecticut coast of the United States. In the East dark spots in a form of “X” or a crescent, especially above by holding a special festival called “žiobrinės“ (žiobris is the they diminish due to pollution, obstructions on the migration Atlantic, they live from the White and Barents Seas down to the lateral line. This predatory fish has well developed teeth. Lithuanian name of the vimba bream), at which the captured routes to the spawning areas, destruction of the spawning Portugal, including the basins of the North and Baltic Seas Salmon can grow really big, up to 46.8 kg, although their fish was cooked or smoked over bonfires. grounds, overfishing, and possibly also due to climate change. as well as Iceland. In Karelia and Sweden, salmon can also be average weight is 4-5 kg and the body length is 50‑100 cm. The European smelts living in the Baltic Sea start found in freshwater lakes. In the Baltic Sea, Atlantic salmons The life span is up to 10 years, but most fish survive for European smelt spawning in early spring, some of them right in the coastal live in the pelagic zone where they chase their prey, while 4‑6 years. (Osmerus eperlanus, Linnaeus, 1758) waters, but most travel in huge shoals into freshwater areas in river deltas or higher upstream. Dependent on the water Juvenile European smelt feed on zooplankton, but as they temperature, the spawning takes place in February-April, grow they target ever larger prey–various crustaceans, in- over a sandy or gravel substrate. The females produce 8 000- cluding shrimps and small fish, for instance, juvenile sprat, 50 000 yellow eggs that stick to the substrate. The larvae Baltic herring or cod. hatch in 3‑5 weeks and drift downstream into the estuaries. Smelts themselves are desirable prey to many fish: they Smelts are pelagic fish therefore their body colour is are hunted by eels, pikes, perches, pike-perches, eelpouts, typical to pelagic species with the light lower parts and and even some cyprinides would not miss an opportunity silvery-grey dorsal side. Such colouration helps to cam- to feast on juvenile smelts. Smelts are often captured also by ouflage against predators. The mouths are equipped with cormorants and other fish feeding water birds. many sharp teeth adapted to grasp the prey. Smelts grow

102 THE BOOK OF THE SEA 103 The water column In Lithuania, salmon breed in their native rivers in In comparison with other duck species wintering in the October-November, as the water cools down to 5–6 °C, by Baltic Sea, the goosander is more likely to choose fresh or digging the so-called nests, which are furrows in the sub- brackish water bodies to spend the cold season: open stretches strate up to 1.5 m long and 0.5 m wide. They release and bury of rivers and streams, lakes and the Curonian Lagoon. Usually some 8‑10 thousand, sometimes up to 30‑40 thousand large it would move into the coastal waters of the Baltic Sea from eggs reaching 5–7 mm in diameter, thus hiding and protect- the Curonian Lagoon if the latter freezes over. Somewhat larg- ing them. After the spawning, salmon return to the sea–they er flocks wintering in the coastal zone of the sea are registered breed up to five times in their lifetime, although few fish in front of the continental coast, where up to 5 000 wintering make it even to the third or fourth reproduction round. individuals have been counted in the recent years. Within Young salmon set off for the sea on their first year or stay in the last decade or so, the numbers of goosanders spending the river for 2-6 years, and upon reaching the sea, they start winters in Lithuanian waters have declined slightly. to feed intensively and quickly gain weight. A trend registered all across the Baltic shows the in- Goosander Various peoples inhabiting the Baltic coasts were using creasing numbers of birds on the wintering grounds in front salmon for food as early as 6 000 years ago, and in the territory of stone and rocky shores and declining wintering stocks in of Lithuania–at least since 3 000 B.C. These very valuable fish lagoons and enclosed bays. In the entire Baltic Sea, goosand- considered a royal delicacy are served salted, dried, hot-smoked ers choose very shallow waters, usually under 5 m deep. Arctic loon or cooked according to countless sophisticated recipes. According to its food preferences, the goosander is a fish-feeding (ichthyophagous) species, whose diet consists Goosander primarily of fish and, to much lesser extent, of other aquatic (Mergus merganser, Linnaeus, 1758) animals. Its bill is adapted to such type of food, equipped with serrated edges that provide a better grip on slippery fish. A species that both breeds and winters in Lithuania. The population annually breeding in our country consists of some Red-throated loon and Arctic loon 1 000 pairs. This bird is listed as Category 5 (restored species) (Gavia stellata, Pontoppidan, 1763; of the Lithuanian Red Data Book. The nests are built in hollow Gavia arctica, Linnaeus, 1758) trees, various openings and cavities (between boulders, under the roots of trees, etc.), but the birds also successfully occupy Just as marine ducks, loons breed in freshwater bodies but customised nest boxes. The breeding population is healthy move to the sea for wintering. and keeps growing. The goosander is the largest of the three The red-throated loon is the northernmost loon species of the so-called “sawbill ducks” wintering in Lithuani- species breeding in the lakes and pools of various sizes in an waters (the other two are the smew (Mergellus albellus) and the Arctic tundra. The start of the breeding season highly red-breasted merganser (Mergus serrator)). depends on the thawing of the snow cover. These birds Red-throated loon

104 THE BOOK OF THE SEA 105 The water column are solitary breeders, and only large lakes may host a few Loons are excellent swimmers capable to dive deep and In Lithuanian waters of the Baltic Sea, three represent- breeding pairs. long in pursue of their main prey–small fish. Because of this atives of the auk family can be observed relatively often: The Arctic loon has a much wider distribution range hunting pattern they often get entangled in stationary fishing the razorbill (Alca torda), the common murre (Uria aalge) than the red-throated loon. A few pairs regularly breed also nets in the territories where their wintering grounds overlap and the black guillemot (Cepphus grylle). Speaking of these in Lithuania. In our country, it is enlisted in the national Red with intense fishery zones. birds, the great auk (Pinguinus impennis) could also be Data Book as Category 1 (endangered) species. The biggest The populations of both species have been declining mentioned. It was a large (some 80 cm tall) flightless bird threat faced by the pairs breeding in remote lakes of Lithua- recently, the main threats being disturbance and depredation that once lived in the North Atlantic–a member of the nia is disturbance caused by recreational visitors. at the breeding grounds, accidental catches in fishing nets same family and close relative of the razorbill which can Similarly to grebes, loons are clumsy on the dry land, and oil pollution at the wintering grounds. be observed in Lithuania. The mass extermination of these therefore they build their nests as close to the water as birds for their downs and plundering of their eggs–at first possible. The males are not very different from the females Great crested grebe for food and then for collections–resulted in the complete by appearance. In breeding plumage, the red-throated loon (Podiceps cristatus, Linnaeus, 1758) amphibians. Contrary to many sea ducks, the wintering extinction of this species in the middle of 19th century. is distinguished by a bright brown patch on its throat and distribution of great crested grebe is less predictable, because The last known breeding pair was killed in 1844 on an islet grey colour on the rest of its neck and head. The Arctic loon In Lithuania, this bird is observed all year round, the breed- the birds aggregate at the sites where their main prey–small adjacent to Iceland. in breeding plumage is also difficult to mistake for another ing population reaching up to 20 000 pairs. It breeds in the fish, are abundant. Usually grebes do not produce large Auks, especially, the common murre, often breed in species. Its head and back of the neck are grey, while the inland water bodies: lakes, ponds, reservoirs, etc. The nest is aggregations at the wintering grounds, they spent winters large colonies on coastal cliffs, teaming up with other co- throat is covered with a large black patch, the sides of the always built at the edge of the water, among aquatic vegeta- dispersed, in solitude or small groups. lonial seabird species. The breeding density of murres may neck bear black stripes while the black back is decorated tion, because the bird is almost incapable of walking on dry reach up to 20 pairs per square metre. Black guillemots nest with white spots. In their winter plumage, both species land. During the breeding season, this grebe is character- Auks solitarily or in small colonies. The breeding sites are located loose that distinctive colouration and can be easily confused. ised by its feathery head and neck decorations and complex on ledges of the cliffs, between pieces of rocks or in wider The red-throated loon differs from the Arctic loon by its bill courtship behaviour. In the past, it was intensively hunted Auks are sometimes called the penguins of the Northern cracks. The nests are very basic or sometimes non-existent. pointing slightly upward (the other species has a horizon- for its decorative feathers. The winter plumage is unimpres- Hemisphere. Contrary to penguins, they can fly by frequent- Razorbills and common murres lay one egg in a clutch, black tal bill) and somewhat lighter neck colour. In addition to sive, predominated by white colour and shades of grey. ly flapping their relatively small wings, however, many other guillemots may produce 1-2 eggs. that, the red-throated loon is a little smaller than its relative. Grebes winter at sea, therefore they can be seen in the features, such as the appearance (with predominant black, dark In Lithuanian waters, auks are observed only outside the Nonetheless, because of great similarity, both species are Baltic coastal waters only outside the breeding period. In winter, brown and white colours), upright posture on the dry land and breeding season, in October‑April. In this period the flying often counted together during various censuses in order to this is the only grebe species abundant along Lithuania’s Baltic excellent diving skills, make them quite similar indeed. Never- auks that are in their winter plumage are very difficult to avoid misidentification. coast. Some 1 500‑2 000 wintering individuals are counted theless, the two bird groups are not closely related. Unlike many distinguish to a non-expert observer, because all the three In the Baltic Sea, loons are usually observed as soli- annually in Lithuanian coastal waters. In the inland waters, only other bird species mentioned in this book, auks rely primarily species are of about the same size, body shape and have tary individuals, less often in small and loose groups. Only solitary birds or small groups are observed in winter. on their wings rather than their feet to gain speed underwater. similar flight patterns. Only black guillemots have much during migration these birds can be frequently seen passing The great crested grebe is a typical fish-feeder, its main They are offshore, or pelagic, species seldom seen from the lighter winter plumage compared to razorbills or murres, or resting in larger groups. Loons winter both in shallow diet consisting of small fish that these birds actively chase shore, except for the breeding grounds. The can dive very deep- with white and grey colours prevailing. The easiest way to coastal waters and offshore, wherever they find enough food. underwater. It can also feed on small invertebrates and ly, over 100 m, but usually feed at the depths up to 30 m. distinguish a murre from a razorbill is by the shape of the

106 THE BOOK OF THE SEA 107 The water column bill: common murres have slender and sharp bills, while independently and is equipped with 10 times more neural those of razorbills are bulky, deep, compressed on the sides cells than the whiskers of land animals! and rounded at the tip. Grey seals assemble into large aggregations for breeding, Razorbills are widespread in Europe, East Canada and moulting and resting, usually on ice or remote islets away Greenland. They also breed in the Baltic Sea on its rocky from humans. In the Baltic Sea, they grow up to 1.6‑2.1 m, shores of Sweden, Finland, Russia and Estonia. Common the females reaching 100‑180 kg, while the males can weigh murres of the Baltic Sea breed only in Sweden, however, they about 300 kg. This is the largest mammal of the Baltic Sea. have a very broad global range, nesting on the coasts of the The females live some 30-40 years, the males–about 10 years Pacific, Atlantic and Arctic Oceans. Black guillemots, al- less. The cows reach sexual maturity at the age of 4‑5 years. though also breeding in the Baltic Sea, are widespread much The skin of the grey seal is dark, ranging from dark grey or further north than their other two relatives of the auk family– brown with patches to black. Black guillemot their nesting grounds reach such remote northern territories The diet of Baltic grey seals highly depends on the sea- as Svalbard and Franz Josef Land. Black guillemots often son and fish abundance. It consists of flatfish, Baltic herring, winter right next to the edge of the ice cover, even in remote cod, sandeels, smelts, shorthorn sculpins, gobies, stickle- Arctic areas. backs. An adult seal can consume some 10-30 kg of fish per All auks usually feed on fish by actively pursuing them day. While hunting, seals can submerge up to 100 m deep underwater. Because of that these birds often get entangled and stay underwater for up to 20 min. in stationary nets if their feeding areas overlap with com- In the Baltic Sea, grey seals moult in April-June, on mercial fishery zones where stationary nets are used. floating ice or at land-based rookeries, while their breeding Common murre and mating takes place in late February-March. The females Grey seal give birth to one, sometimes two pups. The grey seal pups (Halichoerus grypus, Fabricius, 1791) weight 12‑15 kg at birth. They are covered in white soft fur which is replaced by adult fur within 1-2 months, although Grey seals are large colonial marine mammals. They are moulting starts already in 7-10 days after birth. characterised by a pointed snout, rounded head, fusiform The suckling period lasts for only 16-20 days, during body and short tail. A thick layer of fat is stored under the which the female ceases feeding and looses some 50-75 kg skin. The main propulsive organs in the water are their hind of her body weight, relying only on the accumulated fat Razorbill legs which have evolved into broad flippers. The front legs reserve. The mother’s milk has a very high fat content (some- are used for steering and breaking. These animals have good times reaching up to 60 %), therefore the pup gains about senses of smell and hearing as well as sensitive whiskers 2.5 kg per day. called vibrissae, which can sense water turbulence pro- The females discontinue nursing very abruptly by swim- duced by fish and even sound waves. Each vibrissa moves ming out to the sea or starting to mate with the males. The

108 THE BOOK OF THE SEA 109 The water column The numbers of Baltic grey seals started recovering only Baltic Sea, Kattegat and Skagerrak is some 6 000 individuals after the bans on hunting and use of some especially toxic strong, while the eastern population covering the coasts of fertilisers in agriculture had been introduced. Nowadays Germany, eastern Sweden and sometimes Poland consists of the Baltic population of the grey seal is estimated at about only about 200 individuals. 30 thousand, although there are suspicions that it could actu- Harbour seals avoid the open sea and inhabit coastal ally be double of that. Baltic grey seals are currently found all banks, closed bays and areas near large river estuaries. They over the Baltic Sea, although they are most widespread in its tend to lead a sedentary lifestyle sticking to their favourite northern parts: the Gulfs of Bothnia, Riga and Finland. habitats and refraining from distant migrations. A prevailing opinion is that grey seals do not live per- The adult males are about 1.9 m long and weigh manently in Lithuanian territorial waters and only arrive to- 70‑150 kg, while the females reach 1.7 m and 60‑110 kg. The gether with the migratory fish. Although their numbers have colour of males and females is usually the same, ranging markedly increased in the last decade, the exact count is not from light grey to dark brown with black spots, however, the available. These seals are most frequently observed in early belly is always lighter. weaned pups usually have reached 40-50 kg by then. As their till they completely recover and accumulate enough fat to spring during the period of intense seal migrations, usually The harbour seal is easy to distinguish from the grey mothers abandon them the pups fast for 1-4 weeks. This be returned to the Baltic Sea. The rescued seals are usual- as single individuals or pairs, less often in small pods. The seal by the shape of its mouth, where the sides of the lips fasting is a critical stage for the grey seal pups, because their ly released into the wild in spring or autumn, when large largest numbers of sightings were registered at the beaches of hang down to produce an inverted “V”. Its head is also fat reserves are only sufficient for a limited period, in which schools of Baltic herring arrive to breed near the shore Palanga, Smiltynė, Melnragė and Nida, as well as at Karklė, shorter and more rounded than that of the grey seal, and they must learn to swim well and to catch fish. The pups making their survival easier. near the cliff of Olando Kepurė. The total of more than 200 resembles the snout of a dog–hence its popular nickname, loose about 30 % of their body mass over that time. Smaller The released young seals are tagged and named. The grey seal sightings have been registered in Lithuania within “the sea dog”. baby seals that failed to accumulate sufficient energy reserve pups born in the museum are named by children. Each the last quarter of a century. The daily diet of the harbour seal consists of 3‑6 kg of risk freezing or starving to death. spring, a competition is announced and children send in fish. They usually feed individually or in small groups in the Each year such exhausted pups are found also on their drawings and proposed names for the seal pups. The Harbour seal coastal waters, although dives of up to 200 m deep have also Lithuanian shores. They are sheltered by the Lithuanian pups born in the wild are named after a particular location (Phoca vitulina, Linnaeus, 1758) been registered. The main food is marine fish: flatfish, Baltic Sea Museum, nursed and eventually released back into the where they were found, such as Palanga, Nemirseta, Preila or or Atlantic herring, cod, eels, sandeels, smelts, etc.–some 30 Baltic Sea. The weakened pups require a special care and Kopgalis. The harbour seal is the most widespread seal species in the fish species altogether– but they would not miss an opportu- diet. They are given particular meals, consisting of minced Although the grey seal has no natural enemies in the Bal- world. It lives in the temperate, subarctic and arctic climatic nity to grab crabs, shrimps and various molluscs, too. herring, fish oil, various vitamins and micro elements. The tic Sea, the size of its population has been changing quite sig- zones of the Northern Hemisphere. The global population The lifespan of females lasts 30-35 years, while that of mixture is tube-fed to the pups, an only a fortnight later, nificantly within the last century an a half. A little more than consists of about half a million individuals. The species is di- males is 20-25 years. The bulls are attached to their protected when their stomachs adapt to this food, they receive their a century ago, there were about 80‑100 thousand of them. The vided into five subspecies. The Baltic harbour seals belong to territories, usually located near the rookeries or migration first fish. Once the youngsters start eating well and the nec- intensive hunting throughout the 20th century and dramatic the subspecies Ph. v. vitulina, whose main population inhab- routes of the cow seals. This way they increase their chances essary quarantine period is over, they are transferred into increase of water contamination at the end of the century have its the coasts of East Atlantic, while the Baltic Sea hosts only to find fertile females. Harbour seals form colonies at their tanks and pools to join their kin. The young seals stay there reduced the population to 3 000 animals. several thousand individuals. The population of western rookeries, however, individual animals always keep certain

110 THE BOOK OF THE SEA 111 The water column distance. Usually seals lie next to the water edge to be able to attack. The burrows shelter the pups from the cold and hide Ringed seals moult in May-June. In the Baltic Sea, these escape quickly. them from predators, such as foxes, thus being essential for seals feed on local fish (cod, Baltic herring, etc.), enriching Harbour seals mate in the water at about the same time their survival. In summer and autumn, when the ice is gone, their diet with some crustaceans. when the young are weaned. The males fight over females, Baltic ringed seals rest on the solitary rocks peaking above In Lithuania this species is found in exceptional cases: however, they are less aggressive than grey seals. In order the surface, little islets, or rocky shores. only two observations have been registered, in 1997 and in to repel other males from their “aquatic” territories and to The females reach sexual maturity at the age of 2003. In both cases dead pups of the ringed seal were found– attract the females, they use vocalisation an specific swim- 4-6 years. The males reach maturity at about the same age, one of them drowned from entanglement in the fishing nets, ming displays. Gestation lasts for about 10.5 months. In the however, they usually get the first mating opportunity at another dead from multiple injuries. Baltic Sea, the pups are usually born in June-July on sandy species is abundant and still increasing or at least stable, the the age of 8-10 years. The males are slightly larger than the The Baltic population of ringed seals has shrunk dra- or gravel beaches. On the East Atlantic coasts, the females Baltic population is small and vulnerable to external impacts, females. The males are slightly larger than the females. The matically throughout the 20th century, dropping from 190– usually come ashore as the tide starts subsiding, in order to therefore harbour seals are protected in the Baltic Sea. overall length of adults is about 115–136 cm, their weight 220 thousand to 5 thousand individuals. The main reasons give birth before the new tide arrives. The newborn pups are reaching 40–65 kg. Ringed seals are believed to live long of the decline are considered to be hunting and sea contam- well developed and capable of swimming right away. Ringed seal lives–up to 50 years. ination with organic chlorides and other toxic substances. The single pup (twins in exceptional cases) is born (Phoca hispida, Linnaeus, 1758) The breading time is closely linked with the thickness In pursuit of rewards in the early 20th century, hunters in devoid of the white baby fur which is shed while still in the and extend of the ice cover in the Baltic Sea. The pups weight Sweden and Finland used to kill about 20 000 ringed seals womb. The newborn pups are 65-100 cm long and weigh The ringed seal is the smallest seal species living in the some 4–4,5 kg at birth which takes place in March-May, the annually. A complete ban on hunting and killing of Baltic 8-12 kg. They spend the first days of their lives mostly in the Baltic Sea. Its name was given due to the skin pattern: the peak being in early April. The southernmost populations ringed seals was introduced only in 1980 in what was then water, closely following their mothers and coming ashore animal is covered in dark fur scattered with light ring- of the Baltic ringed seals produce young a little earlier, in the Soviet Union, in 1986 in Sweden and in 1988 in Fin- only to rest. shaped patches. February‑March. Within the first fortnight of their lives, the land. Limited hunting permissions were restored in 1998 in The mother nurses the pup for 4‑6 weeks with a very The Baltic Sea is inhabited by the Baltic subspecies of the pups learn to swim and dive, and become able to escape Finland and in 2001 in Sweden. Illegal hunting is suspected fatty milk (up to 45 % fat), both in the water and on the dry ringed seal P.h. botnica. Some 75 % of the Baltic population re- predators by travelling from one blowhole to another. The to take place throughout the entire distribution range of the land. During the lactation period, the pup gains about 0.5 kg side in the northern part of the Baltic Sea, mainly in the Gulf nursing lasts for full 5‑7 weeks, until the pups reach about Baltic ringed seal. daily and soon starts an independent life, where it has to of Bothnia. Another part of the population lives in the Gulfs 20 kg. The males remain together with the females through- Ringed seals are also threatened by climate change, learn hunting and survival skills. of Riga and Finland. These seals usually stick to the sea areas out the entire nursing period. leading to insufficiently thick and shorter lasting snow cover, In the Baltic Sea, the harbour seal has practically no that retain ice cover throughout their breeding season. which may increase pup mortality due to hypothermia. There natural enemies, except humans, who hunt them illegally, Ringed seals have a special skill of using their teeth to are concerns, that in the next 3 decades the southern popu- contaminate water and cause incidental drowning in their dig burrows in the snow over the ice cover. Such burrows lations of the Baltic ringed seals might shrink significantly or fishing gear. Only young seals might also be threatened by have several air vents and blowholes, giving access to the wa- disappear completely, as a result of climate change, and only stray dogs, seagulls and ravens. ter straight from the tunnel. The latter are drilled by the seals the Gulf of Bothnia would remain a sufficiently stable habitat. There are only three recorded sightings of this seal themselves using their strong claws, or based on the natural Although the global population of ringed seals is abun- species in Lithuania, the first one from 2005, the other two cracks in the pack ice. One female usually maintains 4‑6 dant, in the Baltic Sea they are considered as a vulnerable cases from 2014. Although the global population of this blowholes which serve as escape routes in case of predator species and subject to protection.

112 THE BOOK OF THE SEA 113 The water column Harbour porpoise all marine mammals, harbour porpoises have to surface for (Phocoena phocoena, Linnaeus, 1758) breathing. Their gestation lasts for 10-11 months, and the Deep water depressions calves are usually born in late spring or in summer. They The scientific name of the harbour porpoise (Phocoena suckle their mothers for 8-12 months. and dead zones phocoena) originates from the Greek word φώκαινα [phōkai- These animals live in moderately cool to cold waters of na], meaning a seal or a big seal. They are one of the world’s the Northern Hemisphere, mainly in the zones of continen- smallest cetaceans, reaching 1.55 m on the average (males tal shelf and coastal waters, close to estuaries. Sometimes up to 1.43 m, females up to 1.58 m) and weighting around they even swim into the rivers. 55 kg (males up to 50 kg, females up to 65 kg). Their life Harbour porpoises are not regular residents of Lithuanian span is about 10-17 years, and the oldest registered animal territorial waters where they are observed only occasionally. Just as the deserts on the dry land, this realm is was 24 years old. These animals live alone or stay in pods of The harbour porpoise is a rapidly declining species more than 5 individuals. Their diet includes herring, capelin threatened with extinction. The Baltic population is estimat- an especially harsh place to survive. These deserts, and sprat. The daily consumption reaches some 4 kg of fish, ed to consist of some 450 individuals. In the past, these ani- which they sometimes hunt in larger groups, driving them mals used to be hunted for their meat and fat. Nowadays, the however, are not being fried by the merciless sun into dense schools. main threats leading to their decline are accidental catches Harbour porpoises are capable of diving to the depths by fishing gear, pollution, eutrophication, disturbance, and and exhausting heat–on the contrary, they are dark of 200-220 m and holding their breath for up to 5 min., shortage of food due to overfishing. Scientists still lack a lot however, usually they take a breath about every minute. As of information about this mysterious Baltic cetacean. and cold. There is no difference between day and night, or spring and autumn. Oxygen, so plentiful in the air we all breathe, is often in shortage down there, so its availability plays the key role in this realm. The “sea snow”, slowly sinking from the surface in complete tranquillity, is deceiving, as it masks continuous changes happening there.

114 THE BOOK OF THE SEA 115 Deep water depressions and dead zones 116 THE BOOK OF THE SEA 117 Deep water depressions and dead zones Deep water dead zones are the seabed areas where the oxygen concentrations are insufficient for most animals. In the Baltic Sea, they usually occur in depressions with the depths exceeding 80‑90 m. At these sites, all organic material is decom- A posed by bacteria which consume in the process all the oxygen available in the B bottom sediments and demersal water layers. Without these resources, no aquatic organism breathing dissolved oxygen can survive at the bottom, therefore in the deep water dead zones one would almost never find the usual benthic fauna: bivalve and gastropod molluscs, crustaceans or echinoderms, A Cod such as starfish. The only permanent inhabitants of B Relict isopod crustacean Saduria entomon these dead zones are Beggiatoa bacteria, recognisable as white spots or mats on the seabed. These 200 µm long filamentous bacteria devoid of pigmentation often live in the environments with high concentrations of hydrogen sulphide deadly to most animals. Dead zones had existed also in earlier times, before human activities became significant, however since 1940-50s, with the intensification of agriculture based on the use of various fertilisers, which eventually ended up in the sea, the area of such dead zones has Colonies of Beggiatoa expanded tenfold. Ever increasing quantities of nutrients reaching the sea provoked bacteria on the surface of eutrophication. The latter is characterised by the accelerated summer algal blooms, the sea bottom which presently are considered to be one of the major ecological problems of the Baltic Sea. In autumn, as the water cools down and the blooms are over, the dead microscopic algae sink to the seabed. In the spotlights of submarine survey cameras,

118 THE BOOK OF THE SEA 119 Deepp w wataerter de dpressionsepressions and daneadd zonesdead zones Beggiatoa bacteria usually live on the surface of bottom sediments. This stratum separates the deeper sediment layers, devoid of oxygen and rich in hydrogen sulphide, from the lowest layer of water which still contains some oxygen. These bacteria are capable of “relocating” from one environment into another–they “collect” hydrogen sulphide from the deeper layers of sediments, then migrate to the seabed surface to oxidise it with the oxygen extracted from Colonies of Beggiatoa the nitrates available there. They also tend to store nitrates bacteria at the depth of 116 m “for a rainy day”, when no oxygen might be around, in order in Lithuanian territorial to retain capability to oxidise hydrogen sulphide even then. waters of the Baltic Sea By doing so, the bacteria lock up large quantities of nitrates on the seabed and help to mitigate eutrophication at the sea Filamentous chemotrophic bacteria surface. (Beggiatoa,Trevisan ,1842) Scoloplos armiger, Müller, 1776 they appear like snowflakes, therefore such massive descent is sometimes called The genus Beggiatoa was named after Italian medic and the “sea snow”. In oceans, this “snow” might be the key food source to many benthic botanist F. S. Beggiato. The bacteria are filamentous by shape, Scoloplos armiger is an annelid of the class Polychaeta (bristle organisms, but in the deep water dead zones of the Baltic Sea, the only organisms and they are known since the middle of the 19th century. worms), whose red or red-brown elongated body reaches up awaiting it are bacteria. Only on rare occasions, under persistent hurricane-strength They grow by cell division. As one of the cells in a filament to 12 cm and consists of 200 or more segments bearing multi- winds, the salty, heavy, and oxygen-saturated North Sea water is pushed into the dies, the filament breaks at that point thus giving a start to tude of short bristles. The eyes are difficult to distinguish, and Baltic and, flowing along the bottom, reaches its central and northern parts. Thus a new filament in the colony. the 9th - 17th segments are equipped with gills. extensive seabed areas are temporarily supplied not only with “refreshed” water These bacteria consume hydrogen sulphide, toxic to suitable for marine life, but also with some North Sea inhabitants arriving with these most benthic animals, by oxidising it with the oxygen ex- water masses, such as polychaetes Scoloplos armiger. For a short period, the dead tracted from nitrates. The seabed colonies of these bacteria zones spring into life, they also attract mobile relict isopods Saduria entomon, which are easy to recognise by the pale colour which they gain had previously retreated into shallower locations. This revival of the dead zones may because of the accumulated sulphur. As hydrogen sulphide last for a year or two, before the oxygen is depleted and these areas once again turn is often associated with the oxygen depletion invoked by into the realm of bacteria. human activities, and the Beggiatoa colonies avoid higher oxygen concentrations necessary for most other living organisms, they are considered an effective indicator of “disturbed” environmental conditions.

120 THEJŪROS BOOK KNYG OFA THE SEA 121 Deep water depressions and dead zones Being widespread in the North Sea and southern Baltic, the southern regions or central part. At some locations, the these polychaetes can be found in both shallow sublitto- density of Pontoporeia femorata reaches over 2 000 individ- ral and bathyal (up to 2 000 m deep) zones, and even in uals per sq. m. They can live in deep and cold zones of the estuaries. Scoloplos armiger live in all types of soft depos- Baltic Sea, at the boundaries of deep water dead zones, and its, however, they prefer silt bottoms where they burrow they can tolerate low water salinity. 10‑15 cm deep and produce burrows lined with mucus. In By filtering water and feeding on the remains of sunk- central Baltic Sea and Lithuanian waters this bristle worm en phytoplankton and other dead organic matter, these am- is found only in deep zones. Their small, just a few milli- phipods mix up bottom sediments, increase oxygen levels, metres long, larvae are thought to be brought in by saline and regulate the flows of nutrients (nitrogen, phosphorus, water masses. This explains abundance fluctuations of this etc.). They also forage on bacteria and other microscopic species that follow the intensity of the North Sea water organisms. inflow into the Baltic Sea: the bigger the input, the denser the Baltic populations of this worm, and the further north Diastylis rathkei, Krøyer, 1841 they disperse. This unusually shaped crustacean is unlike any other crusta- Pontoporeia femorata, Krøyer, 1842 cean living in Lithuanian waters. In the western part of the Baltic Sea, it is the main food Diastylis rathkei Pontoporeia femorata is an amphipod originating from the source of the demersal fish. This species lives on the bottom, Arctic seas and nowadays broadly widespread from the but also rises into the water column. Although in central Arctic Ocean to the Baltic Sea, where it is more common in parts of the Baltic Sea, including Lithuanian waters, it lives exclusively in the deep areas, in some other areas it may also be found in quite shallow waters with the depths of around 10 m. In those locations it demonstrates the negative photo- taxis, i.e. behaviour, when the organisms react to the light by moving away from it. The animals loose this trait when they settle deeper. For instance, in the North Sea this crustacean is a true fan of great depths and can be found up to 250 m below the surface. As all crustaceans, this species undergo ecdysis, but their exceptional feature is that they rise from the bottom to moult and swim in the water column. No scientific explanation for this strange behaviour has been given so far.

122 THE BOOK OF THE SEA 123 Deep water depressions and dead zones Ostracods, or seed shrimps In Japan, the Caribbean and Australia, some species (Ostracoda, Latreille, 1802) of ostracods are called “sea fireflies”, because at night they are capable of emitting a bright blue light. With sufficient Ostracods are one of the most numerous groups of crusta- oxygen supply, this luminescence is produced by reaction of ceans, consisting of about 8 000 species. They are relatively two chemical substances. There are reports, that during the small animals of 0.1‑32 mm, however despite the small size, Second World War, the Japanese army has been using these some species are severe predators, hunting in groups and ostracods in the field to read instructions or military maps. capable of killing a few times larger prey, such as annelids or Large quantities of these organisms used to be collected, fish. Some 40 species live in the Baltic Sea. All of them are desiccated and ground into powder, which could later be small, about a millimetre in size. dampened with a few drops of water to produce light when- Nature conservation An Australian ostracod Australocypris robusta is noto- ever needed. rious for its unusual reproductive features. The spermatozoa Because of their calcium carbonate shell, these or- produced by the males are 3.6 times longer than the body of ganisms preserve well as fossils. The oldest fossils and the the male itself. These ostracods have especially large repro- oldest identified ostracods date back 488‑444 million years. ductive organs where the spermatozoa are stored in a coiled For this reason, they are among the most useful organisms form. Nevertheless, many freshwater ostracods reproduce by for palaeontology, which among other things, analyses the parthenogenesis (from the Greek, parthenos meaning virgin, sedimentation patterns, the age of different rock formations, and genesis meaning creation) rather than sexually. This term and describes climatic conditions that prevailed millions describes such reproduction when an organism develops years ago. from a non-fertilised egg. Parthenogenesis among ostracods Ostracods are also found in the pieces of amber, as is thought to be induced by parasitic bacteria which infect inclusions. The first such piece of amber was found in the the eggs. Such populations consist exclusively of females. Baltic Sea in 2005, with the the ostracods preserved in it dating back 42‑54 million years. This piece of amber contained a freshwater species of ostracod from the genus Cyclocypris. Ostracods are preyed upon by small demersal fish. Cu- riously, some ostracods manage to survive even the passage through the digestive tract of juvenile flatfish, and happily go on with their lives upon ejection with the excrement. For that reason they are considered to be especially good indicators of environmental conditions, little affected by fish populations.

124 THE BOOK OF THE SEA 125 Deep water depressions and dead zones Why is it necessary to protect nature?

The easiest answer to the question why we should protect nature could be put in a simple statement: we, humans, need nature, but nature does not necessarily need us. Nature does not care which species occupy certain niches, which animal communities will settle in a particular territory, what habitats will evolve. Nature is a big whole, shaped by a multitude of different factors, with us, humans, being just one of them. Nature is constantly evolving, and each individual tries to adapt in this changing environment. Changing conditions and ability to adapt to them are the key driving forces of a slow and long process of evolution. As this process goes on, new species occur, and part of the old ones get extinct. Scientists have determined, that in the natural course of evolution, about 15 species would disappear annually. We must admit, however, that human activities affecting nature change various conditions at much faster rate, and many species are unable to adapt that fast. Therefore, according to some scholars, the rates of extinction in some groups of organisms have been accelerated 100 times, and in some others–up to 1000 times or even more. This means that a few tens or even over a hundred species disappear every day. Such rapid loss of biological diversity has been labelled as the “sixth mass extinction event”. The fifth extinction event took place some 65 million years ago. It was then, that the dinosaurs disappeared. It all may sound very abstract, because extinction of species does not happen overnight, and often it takes place far away from us. Or we simply do not notice these species around us, because they have already become very rare or simply are too small to be seen. One such example could be the aquatic warbler, still breeding in Lithuania. This inconspicuous passer- ine bird breads in just five countries world-wide. Experts are concerned that this warbler may soon join the list of extinct species. The estimates are that 95 % of this bird’s population has been lost within the last 100 years.

126 THE BOOK OF THE SEA 127 Why is it necessary to protect nature? 128 THE BOOK OF THE SEA 129 Why is it necessary to protect nature? The principles and tools of nature conservation

A Baltic coast in the Gulf Dependent on the approach, the roots of nature conservation could be found in religious of Finland teachings of the ancient scripts, cherishing and protection of the holly sites, or hunting preserves, accessible only to a handful of the privileged ones. Yet there is a common agreement that the modern principles of nature conservation were first applied in the 19th century, with the establishment of the world’s first Yellowstone National Park in the United States in 1872. A little later, in the early 20th century, the designation of protected territories had become more active, as had the conservation movement itself. The then U. S. President Theodore Roosevelt was confronted with two different approaches to There could be many different reasons, why we should protect and cherish natural di- nature conservation, which remain relevant even nowadays. During a picnic in the wild versity. Experts working on the ethics of nature conservation, distinguish the following main together with President Roosevelt, a famous British writer and promoter of wild nature motivational trends: evolutionary, ethical, utilitarian, aesthetic, and economic. John Moore was discussing about the value of wild nature and the need for the govern- The evolutionary arguments place emphasis on the necessity to preserve genetic diversity ment to step in for its protection. At the same time, the President’s Advisor, Gifford Pin- in order to secure the continuity of nature and broad adaptation potential. Conservationists fol- chot, was defending the opinion that nature should be cherished as a valuable resource, lowing the ethical line of thinking insist that the right to survive is universal and applies to every necessary for the present and future generations. Both these attitudes remain viable up living organism, and they also speak about our duty to preserve nature for the future generations. till now. The supporters of the aesthetic approach see the necessity to cherish nature first of all because The first protected territory in Lithuania, Žuvintas Strict Nature Reserve, was established of her beauty and uniqueness. Finally, the camps of utilitarians and economists accentuate the in 1937. The creation of this reserve is usually associated with the name of the most famous practical benefits and the ecosystem services that nature provides. In modern times of the mar- Lithuanian naturalist of the last century Tadas Ivanauskas. ket economy, predominated by consumption culture, the practical benefits represent the most Although the first marine protected territory is considered to be Fort Jefferson in Florida, understandable and acceptable line of arguments to many people. founded in 1935, the true starting point of active efforts to preserve natural diversity in the Finding the most important or the best justified motivation to preserve our nature is marine environment is associated with the First World Conference on National Parks of 1962, hardly a feasible task. What really matters, is for everybody to find their own cause. where maritime conservation was given a special focus. Designation of protected areas and performance of special activities therein is one of the most widespread conservation methods world-wide. The established protected territories

130 THE BOOK OF THE SEA 131 The principles and tools of nature conservation experts recreate the conditions necessary for these factors to kick-in, and thus ensure the survival of rare species and habitats. Control of invasive species is one more conservation tool gaining an increasing importance in the modern globalised world. Alien immigrants can seriously disturb an ecosystem and cause substantial damage. Without natural enemies in the new environment, the invasive species can prove deadly to the local ones, by introducing new diseases or occupying a specific niche in the food web. A good example is the round goby, which was first captured in Lithuani- an waters in 2002, and since has become one of the most abundant species at our coasts. A sea holly in the dunes Gobies are thought to be strong competitors to the local flatfish species and the eelpout. It is of Neringa (Curonian Spit) quite possible, that gobies, being very numerous and consuming large quantities of molluscs, have caused a significant decline in the numbers of wintering sea ducks, competing for the same food. Unfortunately, control of the abundance of invasive species by capturing, introducing natural enemies, or by some other means is practically impossible in marine ecosystems. Restriction of trade in protected species is yet another conservation instrument. This preventive measure is regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the CITES Convention. Trade in plant are provided with nature management plans, indicating special measures aimed to ensure the and animal species or products thereof has become one of the key reasons of their extinc- favourable status of the protected values. In addition, activities, that can produce any negative tion. Corals, sharks and many other marine organisms, included in the CITES lists of trade impact on the protected objects, are restricted. Protected areas also play an important role in restrictions, become a less attractive commodity and thus can be protected from complete public awareness raising, contributing to better knowledge of nature. In Lithuania, protected extermination. areas usually cover both natural and cultural heritage, therefore a harmonised coexistence When certain species occur on the brink of extinction, or when no other means to preserve between human and nature is given a special emphasis. them are possible or feasible, the programmes of breeding in captivity or reintroduction into However, the creation of protected areas is not the only tool in nature conservation. Reme- new habitats of endangered species are implemented. These conservation measures are carried diation of degraded or destroyed habitats is another widespread method, usually integrated out with consideration or broadly agreed criteria, that help to assess, whether the sites desig- with territorial protection. Habitat remediation is more complicated in the marine protected nated for release into the wild are free of threats, and to make sure, that such actions have no areas, therefore it is applied less frequently than on land. negative impact on other local organisms in that area. Consent of the local human inhabitants Following the ecosystem-based approach, restoration and maintenance of key ecosystem is also an important precondition for the application of this conservation tool. development factors may also be an option. Storms, fires, grazing, wind erosion or seasonal ice drift are all important factors that certain species are adapted to. For instance, many well known coniferous trees are adapted to natural forest fires, and for some species they are a necessary precondition for propagation by seeds. Wind erosion shapes dune habitats occupied by specially adapted plant and animal species. By applying conservation measures,

132 THE BOOK OF THE SEA 133 The principles and tools of nature conservation Protected marine areas in Lithuania

A range of national protected areas have been designated with the aim to protect marine habitats of Lithuanian coastal waters, which are important from the conservation point of view. They include Baltic Sea Biosphere Polygon and State Marine Reserve of the Baltic Sea. Marine biodiversity is also protected at Curonian Spit National Park and Pajūris (Seacoast) Regional Park, where the Baltic coastal waters comprise a significant part of their territories. Within Lithuania’s exclusive economic zone, the Klaipėda–Ventspils Plateau and the Sambian Plateau are designated as protected areas with the status of a biosphere polygon. In addition to them, back in the year 2000, Birdlife International identified maritime territories, classified as Important Bird Areas (IBAs), which attract significant aggregations of migratory and wintering seabirds. All these protected marine areas are of international importance and constitute a part of the European ecological network of nature protection areas Natura 2000. As many as six protected territories (Baltic Sea and Curonian Lagoon Biosphere Polygons, State Marine Reserve of the Baltic Sea, Curonian Spit National Park, as well as Pajūris and Nemunas Delta Regional Parks) are listed in the HELCOM Marine Protected Areas (MPA) Database. In 2000, Curonian Spit National Park was also included in the UNESCO World Heritage List.

Offshore protected areas Protected areas in Lithuanian Baltic Sea Biosphere Polygon. It was established in 2013 with the aim to protect a valuable waters of the Baltic Sea and segment of the Baltic ecosystem along the Curonian Spit, with the particular aim to preserve Curonian Lagoon waterbird aggregation sites, designated as Special Protection Areas according to the EU legislation, attracting high numbers of migratory species, such as the little gull (Hydrocoloeus minutus) and wintering species, such as the velvet scoter (Melanitta fusca) and the razorbill (Alca torda). This protected area covers 31 959 ha. Its eastern boundary coincides with the

134 THE BOOK OF THE SEA 135 Protected marine areas in Lithuania western boundary of Curonian Spit National Park, while the southern boundary lies along the state border between the Republic of Lithuania and the Russian Federation. This territory is of exceptional importance for velvet scoters and razorbills wintering in the Baltic Sea, as well as for little gulls during their summer migration. Even though the velvet scoter is officially enlisted as vulnerable in the IUCN Red List of Threatened Species, this particular aggregation attracts over 40 000 individuals, therefore Baltic Sea Biosphere Polygon was designated as a Special Protection Area (SPA) of the Natura 2000 network. State Marine Reserve of the Baltic Sea is the only one of its kind in Lithuania, however, A goosander family comes it is huge (covers over 14 000 ha of marine area). The reserve was founded in 2005 to pro- to meet the sea tect a valuable sublittoral ecosystem of the Baltic Sea in the segment between Giruliai and Manciškė. It is important for wintering and migratory aggregations of the red-throated loon (Gavia stellata), the Steller’s eider (Polysticta stelleri), the common goldeneye (Bucephala clangula), the goosander (Mergus merganser), and the little gull (Hydrocoloeus minutus). A reef habitat of the European importance (habitat code 1170) is located on the underwater slope. This protected area also bears the status of a Natura 2000 site. Karklė Marine Reserve. State Marine Reserve of the Baltic Sea borders with another unique protected area rich in biodiversity, Karklė Marine Reserve, which is a part of Pajūris (Seaside) Regional Park. Pajūris Regional Park is situated along the Baltic coastline between Klaipėda and Palanga, more than half of its territory stretching into the Baltic Sea. The parks is an interesting diving ground, offering the possibility to inspect some shipwrecks, enjoy the boulder-dominated seascapes and aquatic life. The segment of coast between Olando Kepurė cliff and Nemirseta features numerous large boulders overgrown with algae and molluscs. These are reefs–a highly protected marine habitat, that provides shelter to many plants and animals, constitutes an important spawning ground and sustains large numbers of wintering birds foraging on molluscs and crustaceans. This area offers protection for especially abundant aggregations of wintering waterbirds: the Steller’s eider (Polysticta stelleri), the common goldeneye (Bucephala clangula), the goosander (Mergus merganser) and the little gull (Hydrocoloeus minutus). Klaipėda–Ventspils Plateau Biosphere Polygon. This is a new protected area in the south-eastern part of the Baltic Sea, over the submarine Klaipėda–Ventspils Plateau. Its major part lies within the exclusive economic zone of Lithuania, the rest being in the territorial sea. It starts some 8 km away from the Lithuanian coastline at its southern borderline and some

136 THE BOOK OF THE SEA 137 Protected marine areas in Lithuania Just as Klaipėda–Ventspils Plateau Biosphere Polygon, this area was designated for the protection of reef habitat–shallower accumulations of bounders towering over the surrounding seabed in various parts of the plateau, featuring rich colonies of mussels and relatively high species diversity of benthic macrofauna. It also attracts large aggregations of wintering long-tailed ducks, velvet scoters and razorbills.

Restrictions of human activities at the marine reserves Migration and wintering periods are especially challenging for birds, because low tem- The local fishermen have peratures and winds, affecting birds during their local flyovers and searches of suitable feed- a special name, “šaktarpas“, ing grounds, drain a lot of energy from them. Any additional disturbance, making them burn for the season when the their energy to move into another area, or pushing them into less favourable feeding grounds, melting ice cover of the weaken their condition and shrink their chances to last through the winter. Curonian Lagoon is already The conservation regimes of the Baltic Sea areas, designated for the protection of too thin for walking but natural values, restrict such human activities that could impair the status of wintering and still obstructs boating migrating waterbird populations or damage natural marine habitats. Within these territories, hunting on waterfowl is prohibited, while in the periods of migration and wintering, 21 km away at the northern boundary which coincides with the border between the Republic fishing by stationary nets is strictly regulated in order to avoid entanglement and drowning of Lithuania and the Republic of Latvia. The area of the protected zone is about 31 610 ha. of the diving birds. This area was designated to protect a deep reef habitat of Community Interest. Because of Protection of natural values of the Baltic Sea is a shared responsibility of several insti- great depths, the territory is free of macroscopic algae common on shallow reefs, but it hosts tutions. For instance, monitoring of the status of protected bird species is performed by the a typical reef community–dense colonies of mussels, the Mytilus sp., with the associated fauna: administrations of Curonian Spit National Park and Pajūris Regional Park. Control of marine the bay barnacle Amphibalanus improvisus, the bryozoan Electra crustulenta, etc. Wintering natural resources is a task shared by inspectors and officers from the State Environmental waterfowl are also abundant: the velvet scoter (Melanitta fusca), the razorbill (Alca torda), and Protection agencies and the Fisheries Service under the Ministry of Agriculture. the long-tailed duck (Clangula hyemalis). In order to preserve this reef habitat of Community Interest along with the wintering aggregations of waterfowl, this biosphere polygon is planned Other protected areas related to the Baltic Sea to be included into the Natura 2000 territorial network. Curonian Spit National Park. Right next to Baltic Sea Biosphere Polygon, Lithuania’s Sambian Plateau Biosphere Polygon. This is a territory encompassing part of a unique largest protected marine area, lies Curonian Spit National Park, which is one of the most marine plateau of the south-eastern Baltic Sea with a characteristic seabed profile and a mosa- unique protected areas of our country. It covers the almost 50 km long Lithuanian part of the ic pattern of boulders, morainic clay loams and sandy loams. The polygon lies in the exclusive Curonian Spit together with the coastal waters on both sides: in the Curonian Lagoon and economic zone of Lithuania, some 17 km away from the shoreline, and its southern boundary the Baltic Sea. The national park was founded in 1991. Its main protected natural values in- overlaps with the state border between the Republic of Lithuania and the Russian Federation. clude the great dune ridge with the ancient drifting parabolic dunes, the sheltered inter-ridge The area of this protected territory is about 21 120 ha. sand plains along both coasts, the humid dune slacks and foredunes, specific vegetation and

138 THE BOOK OF THE SEA 139 Protected marine areas in Lithuania animal life, ethnographic fishermen houses and historical villas, the relics of ancient settlements buried by the sand, and many other objects. References The arid and poor sandy soils of the Curonian Spit, frequent and fast weather fluctuations, along with the strong winds, determine the diversity of flora and fauna of the park. The White Sea-Baltic avian migratory route lies along the length of the Curonian Spit, used by some 15 million birds annually. In winter, many thousand strong wintering aggregations of waterfowl settle in the Baltic Sea areas in front of the Curonian Spit. Sea-feeding species include the long-tailed duck (Clan- gula hyemalis), the red-throated loon (Gavia stelata) the goosander (Mergus merganser), the Aquascope. Learn more about the sea! (2014). Bilgin S., Ozen O., Samsun O. (2009). Sexual seasonal growth common goldeneye (Bucephala clangula), the tufted duck (Aythya fuligula), the great crested http://vattenkikaren.gu.se/defaulte.html variation and reproduction biology of the rock pool prawn, grebe (Podiceps cristatus), the Steller’s eider (Polysticta stelleri), and the white-tailed eagle BACC Author Team (2011). Assessment of Climate Change for Palaemon elegans (Decapoda: Palaemonidae) in the (Haliaeetus albicilla) can often be seen gliding over the area. the Baltic Sea Basin. Regional Climate Studies, Springer- southern Black Sea. Scientia Marina 73(2), 239–247. On the sea-facing side of the park, Neringa Marine Reserve was established for the pro- Verlag Berlin Heidelberg, XXII, 474 p. Bird C.J., Saunders G.W., McLachlan J. (1991). Biology of tection of shallow sublittoral seascape ecosystems including habitats of Community Interest. Bacevičius E. (2002). Ilgasnukiai ruoniai - gyvasis Baltijos Furcellaria lumbricalis (Hudson) Lamouroux (Rhodophyta: The national park is included in the Natura 2000 ecological network. paveldas. Mokslas ir gyvenimas, 12 (540). Gigartinales), a commercial carrageenophyte. Journal of The Curonian Lagoon. This is a shallow freshwater lagoon of the south-eastern part of the http://ausis.gf.vu.lt/mg/nr/2002/12/12il.html Applied Phycology, 3: 61–81. Baltic Sea. The Curonian Lagoon is rich in rare species and habitats. It includes marine habitat Bacevičius E. (2013). Blyškusis Baltijos gelmių senbuvis. Bitinas A. (2011). Paskutinysis ledynmetis rytinės Baltijos types of Community Interest listed as “1130 Estuarties” and “1150 Coastal lagoons”. The lagoon http://albatrosas.lt/Blyskusis-Baltijos-gelmiu-senbuvis- regione. Klaipėda University publishing, 154 p. is an important spawning ground and migratory route to many fish and lamprey species. Mi- p639.html#.VvJOGEelTDc Bonnie S. (2013). Bladderwrack Herb Effects. gratory bird species, including the Bewick’s swan (Cygnus columbianus bewickii), the northern Bagdanavičiūtė I., Kelpšaitė L., Daunys D. (2012). http://livestrong.com/article/113644-bladderwrack-herb- pintail (Anas acuta), the goosander (Mergus merganser), the smew (Mergus albellus), the little Assessment of shoreline changes along the Lithuanian effects/ gull (Hydrocoloeus minutus), and the white-tailed eagle (Haliaeetus albicilla), form aggrega- Baltic Sea coast during the period 1947–2010. Baltica 25: Centre for Marine Evolutionary Biology. Idotea balthica. tions of international importance in or around this water body. In order to preserve its ecosys- 171–184. http://cemeb.science.gu.se/research/target-species- tem, Curonian Lagoon Biosphere Polygon was established in 2009. Part of the water area of Bajerčiūtė A., Pupienis D. (2012). Baltijos jūros hidrologinį imago+/idotea-balthica/ the Curonian Lagoon falls under the territory of Curonian Spit National Park and Nemunas režimą formuojančių hodrometeorologinių veiksmų analizė Chivian E., Bernstein A. (eds.) (2008). Sustaining life: How Delta Regional Park. The Curonian Lagoon is included in the Natura 2000 ecological network 1960–2009 m. Geografija, 48 (1): 12-21. human health depends on biodiversity. Center for Health and because of its species and habitats of Community Interest. Bellafiore D., Gulbinskas S., Umgiesser G., Ferrarin C., the Global Environment. Oxford University Press, New York. Zemlys P. (2013). Investigation of saline water intrusions Damušytė A. (2011). Lietuvos pajūrio geologinė raida into the Curonian Lagoon (Lithuania) and two-layer flow poledynmečiu. PhD thesis Vilnius University. in the Klaipėda Strait using finite element hydrodynamic FAO Corporate document repository. Synopsis of biological model. Ocean Science 9 (1), 573-584. data on the common shrimp (Crangon crangon). http://fao.org/docrep/005/ac765t/ac765t03.htm

140 THE BOOK OF THE SEA 141 References Fava G., Zangaglia A., Cervelli M. (1992). Ecology of Idotea HELCOM (2010). Towards an ecologically coherent network Kinne O. (1971). Marine Ecology. Wiley Interscience, London. Ornes S. (2013). Mussels’ sticky feet lead to applications. baltica (Pallas) populations in the lagoon of Venice. of well-managed Marine Protected Areas – Implementation Leppäranta M., Myrberg K. (2009). Physical Oceanography of PNAS, 110 (42): 16697-16699. Oceanologia Acta, 15(6): 651–660. report on the status and ecological coherence of the the Baltic Sea. Geophysical Sciences, Springer-Verlag Berlin Österblom H., Casini M., Olsson O., Bignert A. (2006). Galkus A. (2003). Vandens cirkuliacija ir erdvinė drumstumo HELCOM BSPA network. Baltic Sea Environ. Proc. No. 124B. Heidelberg, XXIX, 378 p. Fish, seabirds and trophic cascades in the Baltic Sea. dinamika vasarą kuršių marių ir Baltijos jūros Lietuvos HELCOM (2013). Climate change in the Baltic Sea Area: Lesutienė J., Gasiūnaitė Z.R., Strikaitytė R., Žilienė R. (2014). Marine Ecology Progress Series 323: 233–238. akvatorijose. Geografijos metraštis, 36 (2): 48-60. HELCOM thematic assessment in 2013. Baltic Sea Environ. Trophic position and basal energy sources of the invasive Price R.K.J., Uglow R.F. (1979). Some effects of certain metals on Geppettia L., Tongiorgi P. (1967). Nocturnal Migrations of Proc. No. 137. prawn Palaemon elegans in the exposed littoral of the SE development and mortality within the moult cycle of Crangon Talitrus saltator (Montagu) (Crustacea, Amphipoda). Italian HELCOM (2013). HELCOM Red List of Baltic Sea species in Baltic Sea. Aquatic Invasions, 9 (1): 37–45. crangon (L.). Marine Environmental Research, 2: 287–299. Journal of Zoology, 1 (1): 37-40. danger of becoming extinct. Baltic Sea Environ. Proc. No. 140. Lippson A.J., Lippson R. (1984). Life in the Chesapeake Bay. Ruskule A., Kuris M., Leiputė G., Vetemaa M., Zableckis Š. Gleick P.H. (1996). Water Resources. In: Encyclopaedia of Herbwisdom.com. Bladderwrack (Fucus vesiculosus). http://chesapeakebay.net/fieldguide/critter/barnacles (2009). Atrask Baltijos jūrą, spalvingas ir verdantis jūros Climate and Weather (ed. S.H. Schneider), Oxford University http://herbwisdom.com/herb-bladderwrack.html MarLIN (2006). BIOTIC - Biological Traits Information Catalogue. gyvenimas. Baltic environmental forum, Latvia, 1–82. Press, New York, vol. 2: 817-823. Iniciatyva „Tvari jūra“. Baltijos jūra – kam ji rūpi… . (2014). Marine Life Information Network. Plymouth: Marine Seaweed Industry Association. Furcellaria lumbricalis. (2014). Haahtela I. (1990). What do Baltic studies tell us about the http://vembryrsig.hallbarahav.nu/?lang=lt_LT Biological Association of the United Kingdom. https://seaweedindustry.com/seaweed/type/furcellaria- isopod Saduria entomon (L.) Ann. Zool. Fennici, 27: 269–278. Invasive Species Compendium. Palaemon elegans (Rock http://marlin.ac.uk lumbricalis Harff J., Björck S., Hoth P. (ed-s) (2011). The Baltic Sea Basin. shrimp). (2011). http://cabi.org/isc/datasheet/70617 MarLIN, 2014. The Marine Life Information Network. Smith R. J. (2014). Ostracod Research at the Lake Biwa Museum, Central and Eastern European Development Studies Jankauskienė R., Safonovienė A. (2009). Distribution of sand http://marlin.ac.uk Japan. Amazing Ostracod Facts. (CEEDES). Springer-Verlag, Berlin Heidelberg, XIII, 449 p. hoppers (Talitrus saltator, Montag, 1808) on the beach of Niiranen S. (2013). Multiple forces drive the Baltic Sea food http://lbm.go.jp/smith/facts.html Harris B. (2011). Fucus vesiculosus Bladderwrack. Adaptions of the Lithuanian Baltic sea. Ekologija, 55 (3–4): 196–203. web dynamics and its response to environmental change. Swedish Ice Service. Ice conditions in the Baltic (2007). Fucus vesiculosus. http://bioweb.uwlax.edu/bio203/2011/ Jarmalavičius D., Pupienis D., Žilinskas G. (2014). Sea level Summary of Doctoral thesis, Stockholm University, 29 p. http://smhi.se/oceanografi/iceservice/ice_condition.htm harris_benj/adaptation.htm# fluctuation and shoreline evolution on decadal time scale, NOBANIS – European Network on Invasive Alien species. Telesh I., Schubert H., Skarlato S. (2011). Revisiting Remane’s Harvey Ch. J., Cox S. P., Essington T.E., Hansson S., Kitchell Lithuanian Baltic Sea coast. Journal of Coastal Research, 70: Gateway to Information on Invasive Alien Species in North concept: evidence for high plankton diversity and a protistan J.F. (2003). An ecosystem model of food web and fisheries 164-169. and Central Europe. http://nobanis.org species maximum in the horohalinicum of the Baltic Sea. interactions in the Baltic Sea. 60 (5): 939-950. Jarmalavičius D., Satkūnas J., Žilinskas G., Pupienis D. (2012). Olenin S., Daunys D., Bučas M., Bagdanavičiūtė I. (authors of Marine Ecology Progress Series, 421: 1–11. HELCOM (1986). Water Balance of the Baltic Sea. Baltic Sea Dynamics of beaches of the Lithuanian coast (the Baltic Sea) compilation) (2012). Lietuvos Baltijos jūros aplinkos būklė: Telesh I., Schubert H., Skarlato S. (2013). Life in the salinity Environ. Proc. No. 16. for the period 1993–2008 based on morphometric indicators. preliminarus vertinimas. Klaipėda University publishing, 74 p. gradient: Discovering mechanisms behind a new biodiversity HELCOM (2009). Biodiversity in the Baltic Sea – An integrated Environmental Earth Science, 65 (6): 1727–1736. Omstedt A., Elken J., Lehmann A., Leppäranta M., Meier H.E.M., pattern. Estuarine, Coastal and Shelf Science, 135: 317-327. thematic assessment on biodiversity and nature conservation Jurgelėnaitė A., Šarauskienė D. (2007). Klaipėdos sąsiaurio Myrberg K., Rutgersson A. (2013). Progress in physical The Exotics Guide. Non-Native marine species of the North in the Baltic Sea. Baltic Sea Environ. Proc. No. 116B. pralaidumo pokyčio įtaka jūros vandens prietakos į Kuršių oceanography of the Baltic Sea during the 2003–2014 period. American Pacific Coast. Mya arenaria. (2014). HELCOM (2009). Eutrophication in the Baltic Sea – marias procesui. Energetika, 53 (2): 52–56. Progress in Oceanography 128: 139–171. http://exoticsguide.org/mya_arenaria An integrated thematic assessment of the effects of nutrient Khlebovich V.V. (1968). Some peculiar features of the Orav-Kotta H., Kotta J. (2004). Food and habitat of the isopod The Marine Flora & Fauna of Norway. Seawater.no. enrichment and eutrophication in the Baltic Sea region. Baltic hydrochemical regime and the fauna of mesohaline waters. Idotea baltica in the north-eastern Baltic Sea. Hydrobiologia, Baltic Isopod – Idotea balthica. Sea Environ. Proc. No. 115B. Marine Biology 2: 47-49. 514: 79–85. http://seawater.no/fauna/arthropoda/balthica.html

142 THE BOOK OF THE SEA 143 References Wildscreen Arkive, Sand hopper (Talitrus saltator). Zaiko A. (2005). Balanus improvisus. Baltic Sea Alien http://arkive.org/sand-hopper/talitrus-saltator Species Database. Index Wulff F.L., Rahm L.A., Larsson P. (ed-s.) (2001). A systems http://corpi.ku.lt/nemo/balanus.html analysis of the Baltic Sea. Ecological Studies, 148. Žaromskis R., Pupienis D. (2003). Srovių greičio ypatumai Yang S. (2005). New study finds kelp can reduce level of hormone skirtingose Pietryčių Baltijos hidrodinaminėse zonose, related to breast cancer risk. UCBerkeley News. Geografija, t. 39(1): 16-23. http://berkeley.edu/news/media/releases/2005/02/02_ Žaromskis R., 1996. Okeanai, jūros, estuarijos. Vilnius. kelp.shtml Alca torda 107, 134, 138 Cerastoderma glaucum 53 eagle, white-tailed 140 grebe, crested 24, 66, 106, Alosa fallax 96 Cerastoredma edule 53 eel, European 57, 58, 66, 76, 107, 140 Ammodytes tobianus 57 Chlidonias niger 44 77, 80, 82, 102, 111 green branched weed Amphibalanus improvisus Chroicocephalus ridibundus eelpout 66, 76, 80, 82, 84, 71, 72, 76 72, 138 40 102, 133 guillemot, black 107, 108 amphipod, relict 54, 55 Cladophora sp. 71, 72 eider, Steller’s 66, 85, 86, gull, black-headed 36, 44, 44 Anas acuta 140 Clangula hyemalis 86, 138, 140 137, 140 gull, Caspian 42 Anguilla anguilla 76 Clupea harengus membras 97 Electra crustulenta 138 gull, common 40, 41, 42 auk, great 107 cockle, common 53 filamentous chemotrophic gull, European herring 42, 43 auks 107, 109 cockle, lagoon 53 bacteria 119, 121 gull, great black-backed 42, 43 Aythya fuligula 140 cod, Atlantic 22, 23, 24, 25, gull, little 42, 134, 137, 140 57, 58, 59, 70, 77, 78, 79, flounder, European 22, 48, 57, gull, yellow-legged 42 barnacle, bay 66, 70, 71, 72, 84, 91, 96, 98, 102, 109, 111, 58, 59, 60, 84 gulls 24, 40, 44, 54, 112 73, 138 113, 118 Fucus vesiculosus 39 Beggiatoa 119, 120, 121 Coregonus lavaretus 100 Furcellaria lumbricalis 71 Haliaeetus albicilla 140 bream, freshwater 82 Crangon crangon 54 Halichoerus grypus 109 bream, vimba 84, 101, 102 Cyclopterus lumpus 80 Gadus morhua 77 herring, Baltic 25, 48, 57, bream, white 82 Cygnus columbianus Gasterosteus aculeatus 78 58, 66, 67, 71, 78, 79, 84, bryozoa 138 bewickii 140 Gavia arctica 104 95, 96, 97, 98, 99, 102, 103, Bucephala clangula 137, 140 Gavia stellata 104, 137, 140 109, 110, 111, 113, 114 Diastylis rathkei 122, 123 goby, round 50, 58, 66, 70, 73, Hydrocoloeus minutus carrageen, black 36, 66, 67, duck, long-tailed 62, 66, 70, 84, 85, 86, 109, 133 42, 134, 137, 140 71, 76 86, 138, 139, 140 goldeneye, common 137, 140 Hydroprogne caspia 44 Cepphus grylle 107 duck, tufted 140 goosander 104, 105, 137, 140 Hyperoplus lanceolatus 57

144 THE BOOK OF THE SEA 145 Index Idotea balthica 75, 76 Neogobius melanostomus 84 Saduria entomon 48, 55, 56, stickleback, three-spined isopod, Baltic 66, 75, 76 Neomysis integer 95, 96 57, 78, 86, 118, 120 78, 79 Salmo salar 103 swan, Bewick’s 140 kittiwake, black-legged 42 opossum shrimp 48, 90, salmon, Atlantic 84, 90, 103 95, 96 sand gaper 51, 52, 53 Talitrus saltator 37, 39, 40, 141 Larus argentatus 42 Osmerus eperlanus 102 sand hopper 37, 39, 40, 141 tern, Arctic 44 Larus cachinnans 42 Ostracoda 124 sandeel, great 57 tern, black 44 Larus canus 40 ostracods 124 sandeel, small 48, 57, 58, tern, Caspian 44 Larus marinus 42 103, 111 tern, common 36, 44 Larus michahellis 42 Palaemon elegans 75 Scoloplos armiger tern, Sandwich 44 loon, Arctic 104, 105, 106 Phoca hispida 112 120, 121, 122 terns 44, 54 loon, red-throated 48, 104, Phoca vitulina 111 scophthalmus maximus 58 turbot 57, 58 105, 106, 137, 140 Phocoena phocoena 114 scoter, common 60, 61, 62 lumpfish 66, 80, 81 phytoplankton 24, 25, 72, scoter, velvet 51, 60, 62, 70, Uria aalge 107 91, 93, 95, 122 134, 137, 138, 139 Macoma balthica 51 Pinguinus impennis 107 sculpin, shorthorn 66, 79, 109 Vimba vimba 101 macoma, Baltic 22, 51 pintail, northern 140 seal 24, 26, 58, 75, 91, 98, Melanitta fusca 60, 134, 138 plaice, European 59 100, 103 whitefish, European Melanitta nigra 60 Platichthys flesus 59 seal, grey 90, 109, 110, 112 92, 100, 101 merganser, red-breasted 104 Pleuronectes platessa 59 seal, harbour 111, 112 wrack, bladder 24, 41 Mergellus albellus 104 Podiceps cristatus 106, 140 seal, ringed 26, 112, 113 Mergus merganser 104, 137, 140 Polysticta stelleri 85, 137, 140 shad, twaite 92, 96, 97 Zoarces viviparus 80 Mergus serrator 104 Pontoporeia femorata 122 shrimp, brown 48, 54, 75, 142 zooplankton 24, 25, 57, 58, Monoporeia affinis 54, 55 porpoise, harbour 24, 91, 114 smelt, European 79, 84, 102, 103 79, 91, 93, 95, 98, 102 murre, common 24, 25, 90, prawn, rockpool 75 smew 104 107, 108, 109 sprat, European 24, 78, mussels 22, 23, 66, 67, 69, 70, razorbill 24, 48, 107, 108, 90, 95, 97, 98, 99, 100, 71, 73, 74, 75, 86, 138, 139 109, 134, 137, 139 102, 114 Mya arenaria 51 relict isopod crustacean Sprattus sprattus balticus 98 Myoxocephalus scorpius 79 Saduria entomon 48, 55, Sterna hirundo 44 mysid 48, 90, 95, 96 56, 57, 78, 86, 118, 120 Sterna paradisaea 44 Mytilus sp. 23, 73, 138 Rissa tridactyla 42 Sterna sandvicensis 44

146 THE BOOK OF THE SEA 147 Index Published by:

VšĮ Baltic Environmental Forum Lithuania

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Edition of 1,700 copies

6 THE BOOK OF THE SEA 7 The realms of the Baltic Sea 4 THE BOOK OF THE SEA 5 The realms of the Baltic Sea The word ‘Baltic’ holds many associations of great importance to us: from our childhood memories about splashing in the spatter of the sea and building sand castles, to the Baltic Way–the symbol of our freedom and unity. This is a part of our history and an invaluable treasure. However, contrary to the citizens of many other maritime countries, a few of us are used to fully enjoy the presents of the Baltic Sea, and our acquaintance with it is often limited to summer holidays at the beach.

This book is an opportunity to take a closer look at the Baltic Sea, at its extraordinary and unique life. To see it with the eyes of the authors of different chapters, many of whom have spent countless hours at the sea bottom, on research vessels, observing sea birds or exploring variety of fish.

9 786098 041163

8 THE BOOK OF THE SEA