Heta Rousi Zoobenthos as indicators of marine Heta Rousi | habitats in the northern Baltic Sea of marine as indicators habitats in the northernZoobenthos Baltic Sea Heta Rousi This thesis describes how physical and chemical environmental variables impact zoobenthic species distribution in the northern Baltic Sea and how dis- Zoobenthos as indicators of marine tinct zoobenthic species indicate different marine benthic habitats. The thesis inspects the effects of habitats in the northern Baltic Sea depth, sediment type, temperature, salinity, oxy- gen, nutrients as well as topographical and geo- logical factors on zoobenthos on small and large temporal and spatial scales. | 2020 ISBN 978-952-12-3944-1 Heta Rousi Född 1979 Studier och examina Magister vid Helsingfors Universitet 2006 Licentiat vid Åbo Akademi 2013 Doktorsexamen vid Åbo Akademi 2020 Institutionen för miljö- och marinbiologi, Åbo Akademi ZOOBENTHOS AS INDICATORS OF MARINE HABITATS IN THE NORTHERN BALTIC SEA HETA ROUSI Environmental and Marine Biology Faculty of Science and Engineering Åbo Akademi University Finland, 2020 SUPERVISED BY PRE-EXAMINED BY Professor Erik Bonsdorff Research Professor (Supervisor & Examiner) Markku Viitasalo Åbo Akademi University Finnish Environment Institute Faculty of Science and Engineering Sustainable Use of the Marine Areas Environmental and Marine Biology Latokartanonkaari 11 Artillerigatan 6 00790 Helsinki 20520 Åbo Finland Finland Professor Emeritus Ilppo Vuorinen CO-SUPERVISOR University of Turku Adjunct Professor Faculty of Science and Engineering Samuli Korpinen Itäinen Pitkäkatu 4 Finnish Environment Institute 20520 Turku Marine Management Finland Latokartanonkaari 11 00790 Helsinki FACULTY OPPONENT Finland Associate Professor Urszula Janas SUPERVISING AT THE University of Gdansk LICENCIATE PHASE Institute of Oceanography Assistant Professor Al. Marszałka Piłsudskiego 46 Johanna Mattila 81-378 Gdynia Åland University of Applied Sciences Poland Högskolan Norra Neptunigatan 17 AUTHOR’S ADDRESS 22111 Mariehamn Åbo Akademi University Finland Faculty of Science and Engineering Environmental and Marine Biology Senior Research Scientist Artillerigatan 6 Heikki Peltonen 20520 Åbo Finnish Environment Institute Finland Marine Ecosystems Modelling Latokartanonkaari 11 00790 Helsinki Finland COVER DESIGN, COVER PHOTO AND LAYOUT Linda Svarfvar To my loved ones “Stretching his hand up to reach the stars too often man forgets the flowers at his feet.” Jeremy Bentham SAMMANFATTNING Bottenfauna är goda indikatorer på början av 1990-talet, när den främmande habitatkvalitet samt på miljöstress och och snabbt ökande havsborstmasken miljöförändringar, för de är långlivade Marenzelleria spp. anlände. Samtidigt och reagerar på abiotiska miljöfak- minskade kräftdjuren Monoporeia affin- torer på artnivån. I min avhandling, is och Pontoporeia femorata betydligt i som består av fyra publicerade artiklar, antal eller till och med försvann. Dessa studerar jag effekter av fysiska och förändringar har haft oförnekliga kon- kemiska miljöfaktorer på bottenfau- sekvenser för ekosystemets funktion, på nasamhällens sammansättning i tid grund av de olika egenskaper av arter. och rum. Ytterligare undersöker jag Förändringarna har skett samtidigt med förbindelser mellan bottenfauna och den långsiktiga temperaturökningen, deras habitaten i norra Östersjön. och salinitets- och syrehaltsreduktionen De enskilda undersökningarna i den i området. Resultaten av dessa studier här avhandlingen har utförts på vari- kan användas som verktyg för att eval- erande spatiala och temporala skalor. uera arters respons till förändringar i Specifika arter indikerade olika habi- habitat- och vattenkvaliteten. Ytterligare tattyper. Sedimenttyperna (lera, gyttja, ger dessa resultat information om sta- silt, sand-silt, fin sand, grov sand, grus, tusen av den biologiska diversiteten sten) var viktiga bestämmande faktor- i sedimentvattengränsnittet i Finska er för bottenfauna arternas fördelning, viken under de senaste årtionden. I speciellt på medelstora skalor (mellan framtiden är det viktigt att uppskatta cirka 100-meter och några kilometer). hur förändringarna i artsammansättnin- På en stor landskapsskala (flera kilo- gen påverkar ekosystemets funktion. meter) var de topografiska faktorerna på havsbottnen mer signifikanta vari- abler. I allmänhet ökade antalet arter med ökande topografisk komplexitet, Nyckelord: bottenfauna, bottenfauna- samhälle, indikatorart, habitat, bentiska men de mest komplexa habitaten var sediment-ekosystem, abiotiska miljö- inte de artrikaste. De fysikaliska och faktorer, miljöförändringar, Östersjön. kemiska variablerna (temperatur, syre, näringsämnen och salinitet) påverkade artsammansättningen av bottenfauna signifikant på den finländska kustzonen av Finska viken. På en temporal skala av några årtionden inträffade drastiska Åbo 2020, förändringar i artsammansättningen. Heta Rousi De största förändringarna inträffade i ABSTRACT Zoobenthos are beneficial indicators of occurred in the beginning of the 1990s, habitat quality and environmental stress as the invasive polychaete Marenzelleria and change due to their longevity and spp. arrived and rapidly exponential- how they react species-specifically to ly increased in abundance. At the same abiotic factors. This PhD, consisting of time the crustaceans Monoporeia affin- four published papers, investigates the is and Pontoporeia femorata decreased effects of physical and chemical vari- or nearly vanished from the study sites. ables on zoobenthic species in space These changes have had undeniable and time, as well as the indicator value consequences for the functioning of the of the distinct zoobenthic taxa studied. ecosystem, due to the different func- Furthermore, I investigate the linkages tional traits of the species. The changes between zoobenthos and their habitats in species composition are simultaneous in the northern Baltic Sea. The individu- with long-term temperature increases al studies of this thesis were conducted at as well as with decreases in salinity and different spatial and/or temporal scales. oxygen concentrations in the area. The Specific species were found to be indica- results of the studies can be applied as a tive of different habitat types. Sediment tool to assess species responses to habitat type (clay, mud, silt, sandy silt, fine sand, and water quality changes. In addition, coarse sand, gravel, stones) was found to the results provide information on the be an important driving factor for zoo- status of the biological diversity in the benthic species distribution, especially sediment water interface in the Gulf of on medium (between ~100 – 1000 m) Finland during previous decades. In the spatial scales. On a large landscape future it is critical to assess the impacts scale (several kilometres), seabed topo- of the changes in species composition graphical factors were more significant on the functioning of the ecosystem. drivers. The number of species generally increased with increasing topographi- cal complexity, but the most complex habitats were not the most species rich. Key words: zoobenthos, zoobenthic assemblage, indicator species, habitat, Physical and chemical factors (tempera- seabed ecosystem, abiotic environ- ture, oxygen, nutrients and salinity) in mental factors, environmental change, the water significantly impacted species Baltic Sea distribution along the Finnish coast- al zone of the Gulf of Finland. On the temporal scale of a few decades, drastic Turku 2020, changes have occurred in species assem- Heta Rousi blage composition. The greatest change TABLE OF CONTENTS LIST OF ORIGINAL PAPERS ......................................................................... 1 Contributions to the individual papers ......................................................... 2 1. INTRODUCTION ....................................................................................... 3 1.1. About the Baltic sea – gradients and seasonality ..................................... 3 1.2. Benthic fauna as indicators ..................................................................... 4 1.3. Anthropogenic stress .............................................................................. 5 1.4. Species – habitat connections ................................................................. 6 1.5. Aims of the study................................................................................... 7 2. MATERIAL AND METHODS ................................................................... 12 2.1. Field sampling ...................................................................................... 12 2.2. Statistical analyses ................................................................................ 14 3. RESULTS AND DISCUSSION .................................................................. 17 3.1. Substrate and spatial scales ................................................................... 22 3.2. Temporal changes in species composition ............................................. 25 3.3. Effects of new species to ecosystem structure and functioning .............. 31 3.4. Trophic importance of zoobenthos ...................................................... 32 3.5. Anthropogenic threats and their effects in the marine ecosystem .......... 33 4. IMPLICATIONS AND FUTURE RESEARCH DIRECTIONS .................... 37 5. SUMMARY AND CONCLUSIONS .......................................................... 38 ACKNOWLEDGEMENTS ...........................................................................