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Home , Kelp forest

Kelp Lecture

1. Descriptive 2. Distribution 3. Morphology 4. 5. Life history and reproduction 6. Abiotic factors that influence kelp distribution and growth 7. Biological factors that regulate kelp populations 8. Kelp communities

1 What said…

I know few things more surprising than to see this growing and flourishing amidst those breakers of the western ocean, which no mass of rock, let it be ever so hard, can long resist.

The numbers of living creatures of all Orders whose existence intimately depends on kelp is wonderful… I can only compare these great aquatic forests with the terrestrial ones in the intertropical regions.

Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here from the destruction of kelp.

Charles Darwin, 1 June 1834, Tierra del Fuego, Chile

Laminaria Pterygophora worldwide

Ecklonia

2 Kelp (Brown )

Brown Algae (Phaeophyta) • 1000 species, almost all marine • Includes Sargassum, Padina, kelps • Most common in cold, temperate • Two pigments for : 1) Chlorophyll a (like all ) 2) Fucoxanthin (brown color)

Kelp: Division Phaeophyta () Parts of a kelp • Gas-filled • Rootlike holdfast to attach to substrate • Long hollow stem or stipe • Leaflike blades • Complex life cycle

3 Giant kelp ( pyrifera)

1. In northern Hemisphere a) Occur on rocky bottoms (2 m to 30 m) b) Competitive dominant alga c) Northern limit set by hydrodynamic forces d) Southern limit set by poor substrate & temperature/nutrients conditions

Kelp forests - Where do they occur?

4 II. DISTRIBUTION

1. kelp forests are found in shallow rocky along temperate coasts throughout the world 2. the area of the world’s oceans covered by kelp forests is comparable to that covered by coral reefs. Unlike corals, however, kelp thrives in cool nutrient rich water 3. this explains why the most extensive kelp forests are found on western continental margins, which are areas where extensive occurs.

Worldwide Kelp (Laminariales) Distribution They grow in cold nutrient rich waters

From: Steneck et al. 2001

5 Distribution of Macrocystis and geographic features

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

3. MORPHOLOGY

Apical Meristem

6 3. MORPHOLOGY

1. simple plants consisting of a holdfast, stipe of variable length, vegetative blades, and reproductive blades called sporophylls that produce spores. The primary function of the holdfast is to anchor plant. Thus it differs from a root in that it is not specially adapted to absorb nutrients. Very little in the way of tissue specialization in kelps, or in algae in general. All parts of the plant serve in nutrient absorption and photosynthesis. 2. most photosynthesis occurs in the upper portions of the plant. A plant that extends throughout the it has a need to transport some of food derived from photosynthesis to support growth of lower portions. It does this using specialized cells in the stipe that form a primitive conductive tissue that is unique among the kelps

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

Canopy

Blade Sporophylls

Stipe

Sporophyll

Sorus Holdfast

7 Two sources of productivity in a kelp forest

Macrophyte production

- bathed in nutrients - second fastest growing “plant” on earth - constant production / loss of blades (leaves) - fed on directly by grazing and crustaceans - blades litter reef to create

Plankton influx - , holoplankton, meroplankton - great and diversity of

4. PRODUCTIVITY

1. among the fastest growing plants in the world in either marine or terrestrial habitats. maximum elongation rates in the giant kelp are on the order of 12 -18 inches per day 2. kelp forests are among the most productive communities in the world. Estimates of productivity comparable to tropical rain forests. 3. Interestingly, the of the primary producers is two orders of magnitude less in the kelp forest. which really points to the high productivity of kelp relative to land plants

8 Comparisons between terrestrial forests and giant kelp forests

FOREST TYPE ANNUAL NET PRODUCER LITTER PRODUCTION BIOMASS MASS (dry kg / m2 / yr) (dry kg / m2) (dry kg / m2)

Tropical rain forest 2.2 45 0.2

Tropical seasonal forest 1.6 35 0.5

Temperate evergreen 1.3 35 3.0 forest Temperate deciduous 1.2 30 2.0 forest Boreal forest 0.8 20 4.0

Giant kelp forest 2.2 0.35 0.015

4. PRODUCTIVITY -continued

4. Only about 5-10 % of the is consumed by grazers in either terrestrial or kelp forests. 5. In terrestrial forests most of the biomass accumulates on the ground and persists as litter on the forest floor. 6. There is an order of magnitude less litter on the floor of a kelp forest compared to terrestrial forests

9 4. PRODUCTIVITY - continued 7. Another reason for the small accumulation of kelp litter is that kelps continually sluff organic material which ultimately enters the nearshore . 8. As kelp senesces it releases particulate and dissolved organic matter which provides a significant source of carbon for secondary consumers. 9. Interesting study that used stable carbon isotope analyses in the to confirm the important trophic role of kelp derived carbon in nearshore marine communities.

Percentage of Kelp-Derived Carbon in Kelp Forest Consumers

Suspension Feeders % kelp carbon

Mussel (Mytius edulis) 25 - 40 Soft coral (Alcyonaria. sp.) 40 - 70 Barnacle (Balanus nubilus) 75 – 85 anemone (Metridium senile) 15 - 40 Rock jingle (Pododesmus cepio) 40 - 55 Mysid (Proneomysis sp.) 45 - 60

Detritivores

Amphipod (Anonyx sp.) 70 - 95 (Dermaturus mandtii) 20 - 35

Predators

Rock greenling (Hexagrammos lagocephalus) 40 – 65 Sea star (Leptasterias spp.) 30 - 55 Cormorant (Phalacorcorax peligicus) 35 - 70

10 5. Life history and reproduction Nereocystis Macrocystis

Sorus - Specialized zoospore producing tissue 4 2

1. Blade 1 2. Stipe Sorus 3. Holdfast 4. Pnuematocyst 3

21 From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

Life history and reproduction alternation of generations between a macroscopic spore producing stage = sporophyte, and a microscopic gamete producing stage = gametophyte

Adult sporophyte Juvenile sporophyte

growth Macroscopic

growth Gametophytes release m

syngamy

f Embryonic

Microscopic Zoospores sporophyte settlement

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11 5. LIFE HISTORY AND REPRODUCTION – cont.

4. abiotic factors such as nutrients, temperature and light on growth and reproduction greatly affect life history stages. The production of gametes in the microscopic stage only occurs under certain conditions of light nutrients and temperature. 5. This is particularly important when you think about the that kelp plants recruit to. They start life as a microscopic cell on the bottom not at the surface. It turns out that in most cases the lower depth limit of kelp is determined by the amount of light reaching small stages on the bottom. It has been estimated that the depth that this occurs is where light is reduced to » 1% of that at the waters surface.

6. ABIOTIC FACTORS THAT INFLUENCE KELP DISTRIBUTION & GROWTH . • Nutrients- plants obviously need nutrients to grow and reproduce – Concentrations of nitrogen and phosphorus vary spatially and temporally in coastal waters. – In California, nutrient concentrations generally greater in the north than in the south. – They typically peak in the spring when most upwelling occurs and are at a low in the fall. – Nutrient concentrations can vary greatly from year to year owing to oceanographic events such as El Nino during which time they tend be in very short supply.

12 50 central California 40 N = 5879 30 20 10

0 50 40 southern California gL) / N = 9119 Nutrient-limited m 30 20 10 0

Nitrate ( Nitrate 50 40 Baja California 30 N = 4137 20 10 0 5 7 9 11 13 15 17 19 21 23 25 Temperature (°C)

6. ABIOTIC FACTORS THAT INFLUENCE KELP DISTRIBUTION & GROWTH . • Temperature – generally considered a cool water species – The effects of temperature are difficult to assess in nature because in many temperate areas where kelp grows temperature covaries inversely with nutrient concentration. – In southern California kelp growth is extremely seasonal: greatest in spring when temperatures typically are low and nutrients are high and lowest in the late summer and fall when sea water temperatures are high and nutrient concentrations are low. – Such seasonal variation can disappear during prolonged periods of high temperature and low nutrients such as that that occurs during El Niños. Under these conditions growth and reproduction remains low year round and in the most severe cases results in death

13 Growth as a function of temperature and nitrate concentration

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

Figure 2 Kelpbeds in Southern California

100%

90%

80%

70%

60%

50%

40%

30%

Fraction Fraction of Patches Occupied (%) 20%

10%

0% 1970 1975 1980 1985 1990 1995 2000 2015 Year

14 6. ABIOTIC FACTORS THAT INFLUENCE KELP DISTRIBUTION & GROWTH - continued

3. Light – essential for growth and reproduction • Provides energy for photosynthesis • Influenced by depth, water clarity, season, latitude, vegetation shading • Most severe in early life history stages and transitions (spore, gametophyte, fertilization, sporophyte)

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

15 Growth as a function of irradiance and nutrient limitation

Nutrients replete

Nutrients limiting

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

7. BIOLOGICAL FACTORS THAT REGULATE KELP POPULATIONS

Dispersal • Kelp populations are very dynamic and frequently undergo local extinctions and recolonizations. • Dispersal is a key element to the recolonization process. • Historically, spore dispersal in kelps has been thought to be limited to within a few meters of the parent plant. Such limited dispersal, however, seems incompatible with rapid and widespread recolonization of kelps that is frequently observed.

16 Dispersal

1. Spore dispersal in kelps may not be limited to a few meters. 2. We have measured spore dispersal over distances as large as several kilometers. • Large storms • Turbulent flow 3. Storms also cause massive release of spores 4. Together – release and dispersal during storms leads to long distance dispersal What else??

Nutrients replete

Nutrients limiting

17 1. Competition between different vegetation layers can be important in structuring kelp populations. Most the work that has been done has focused on adults inhibiting juveniles. In general the recruitment of nearly all algae is suppressed underneath dense kelp canopies. Light reduction to 1% 2. Hormonal trickery 3. Layering - Given this high level of shading it is not surprising that there is strong competition for light among the different vegetation layers. 4. There has also been much work done on the effects of intraspecific competition. In general, kelps tend to grow larger, live longer, and produce more spores in lower density stands, though there are some exceptions to this pattern.

Grazing 1. Clearly the number one enemy of kelp are sea urchins. They are the single most important grazer in kelp communities worldwide. They can form large feeding fronts and eat everything in sight (including fiberglass transect tapes), essentially leaving behind a barren ground devoid of macro algae.

2. Urchins don’t always display an active grazing behavior. They are typically sit and wait much like that catch detached pieces of kelp as they drift by.

Questions: • What causes their change in behavior passive sit and wait to active grazing?? • How long are barrens maintained? • What controls urchins?? .

18 Control of grazers (, disease, storms, recruitment)

1. The single most effective predator on sea urchins are sea otters which once ranged from the Kuril Islands in through the Aleutian Is and down the coast of North America to Baja California. Otters eat  25 % of their body weight per day and can effectively eliminate local populations of sea urchins and other shellfish.

2. Islands with sea otters had low densities of urchins and densely vegetated kelp beds. In contrast, islands without sea otters are basically unvegetated barren areas with have high densities of urchins and no macro algae. Thus sea otters have been given this keystone status. The paradigm is that where there are otters you get kelp beds where there is no otters you get barren grounds. This paradigm seems to apply generally in Alaska.

Sea urchins graze on kelp

19 Kelp forest changes

From: Steneck et al. 2001

NORTH ATLANTIC

• Sea urchins and kelp, but no sea otters, but very large predatory !

20 Cod intense for centuries

Urchins rise again

• Fishing technology decreases cod pop. by 1930s

21 Gulf of Maine

Kelp

Urchins

From: Steneck et al. 2001

Nova Scotia

Kelp

Urchins

From: Steneck et al. 2001

22 NORTH PACIFIC/ALASKA

• Sea otters, sea cows, sea urchins and humans

History of fishing in N. Pacific

• Colonization 30,000 years ago, boats used off Japan coast for past 25,000 years • Stellar’s sea cow hunted to extinction (35 feet long, several tons)

23 Sea otters control urchin populations by eating them

History of fishing in Alaska

Humans in Alaska for 9000-10,000 years.

Indigenous tribes began to hunt otters ~ 2500 years ago.

Otter hunting intensified with European arrival in 1700s.

Ecosystem changed to urchin dominated.

24 Otters and urchins Alaska

Urchins

Kelp

From: Steneck et al. 2001

25 Kelp conservation status

• (global temp. increase), human pop. growth, coastal development, oil spills, impacts, non-native sp. invasions all predicted to increase over next 25 years

• Currently, in some areas for urchins coincide with fisheries for urchin predators – a delicate balance

Kelp Forest Communities

26 Kelp forest

Habitat structure

- surface canopy

- subcanopy

- turf

Giant kelp communities

Juvenile finfish Understory algae

Invertebrates Adult finfish Marine mammals

27 "The numbers of living creatures of all Orders whose existence intimately depends on kelp is wonderful… I can only compare these great aquatic forests with the terrestrial ones in the intertropical regions."

"Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here from the destruction of kelp."

Charles Darwin (1860) The Voyage of the Beagle

28 Kelp forests in Northern Hemisphere (south – north)

Sub-canopy species

From: The biology and ecology of giant kelp forests. David R. Schiel & Michael S. Foster.

29 Katlian Bay

Pirate Cove

30 31 32 Kelp conservation status

• Climate change (global temp. increase), human pop. growth, coastal development, oil spills, overfishing impacts, non-native sp. invasions all predicted to increase over next 25 years

• Currently, in some areas fisheries for urchins coincide with fisheries for urchin predators – a delicate balance • One possible solution – Marine Protected Areas established explicitly for conservation

Sea Grasses

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Part of a larger coastal system…

34 WHAT ARE SEAGRASSES?

• Aquatic angiosperms (flowering plants) • Monocotyledenous • a flowering plant with an embryo that bears a single cotyledon (seed leaf).

• Polyphyletic with 4-5 families, ~12 genera and 50-70 species

• • Autogenic engineers

• Found in subtidal AND intertidal (i.e. Zostera marina)

SEAGRASSES AS ECOSYSTEM ENGINEERS

Vegetative • Foundation species & autogenic ecosystem engineers structure provides For example… habitat to invertebrates and Sediment-laden water flows across meadow/bed

Trap sediment Improves water clarity

Less light attenuation=higher photosynthetic rate

35 MORPHOLOGY OF SEAGRASSES

• Varies by species

• Rhizomatous growth pattern • Rhizome extends horizontally in the sediment near the surface • Also develop adventitious roots • Vertical rhizomes develop leaves from a basal meristem

• RAMET=vertical unit of aboveground leaves and below ground roots; modular unit of seagrass growth • Nutrients are translocated from ramet to ramet via horizontal rhizome

• GENET=all ramets that are genetically identical

WHERE SEAGRASSES OCCUR

LOCAL DISTRIBUTION • depth limit=restricted by light availability • shallow depth range limit=restricted by desiccation

Increased light attenuation

GLOBAL DISTRIBUTION • Found in both tropical and temperate coastal systems

36 SEAGRASSES PROVIDE ECOSYSTEM SERVICES & FUNCTIONS Cultural value Regulatory and Economic value

SEAGRASS GOODS & SERVICES Commercial & artisanal fisheries Nursery Habitat for offshore fisheries Food Fodder or bedding for animals Fiber Packing material Fertilizer and mulch Building dikes http://www.juntadeandaluc Coastal protection from erosion ia.es

C Water purification O Interaction with adjacent ecosystems 2 Maintenance of and threatened O species 2 Carbon dioxide sink Cultural, esthetic and intrinsic values Stabilizing sediments

C C C C C C C C O (anoxic sediment) C 2 C microbial activity

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