Ecology BIO C 322 Marine Biomes Biome Set

Ecology (BIO C 322) Marine Biomes

Biome: Set of ecosystems in a region

• On land, a dominant vegetation pattern is the characteristic of a biome. - e. g. tropical rain forest, grassland, etc. • But in aquatic ecosystems, plants are inconspicuous and small; • So, some physical attribute is considered. - e. g. euphotic & aphotic

Oceans: Largest Water Bodies; 3. 5% salt; (Antarctic, Atlantic, Indian, Pacific )

Oceans • Oceans cover 70% of earth surface. • Composition of marine ecosystems determined by waves, tides, currents, salinity, temperature, pressure and light. • Lack of light in the deeps Low primary productivity Deep sea ecosystems dependent on detritus coming from above.

Fish in Deep Sea: Evolutionary Adaptations • Lantern fish – Produce their own light (Biolumenescence). • Angler fish – Movable spine used as a bait to attract prey. • Viperfish and gulpers – Have large mouths; can swallow large prey.

Viper fish Gulper fish Angler fish

Zonation in the Oceans • Littoral or Intertidal – Shoreline between land sea. • Neritic – Shallow water zone on continental shelf. • Pelagic – Whole water body = Neritic + oceanic. • Benthic – From edge of continental shelf to deepest regions. • Zonation w. r. t. light – Euphotic or epipelagic (0 -200 m) and Aphotic (below 200 m).

Littoral Zone E U P H O T I C ----A P H O T I C

Communities of the Continental Shelf • Producers are mainly phytoplanktonic algae diatoms and dinoflagellates. • Also photosynthetic bacteria.

• Consumers (herbivores/carnivores) include: - Holoplanktons (zooplanktons) – Entire life cycle planktonic; in open oceans; copepods (most abundant animals in world), jellyfish. - Meroplanktons (zooplanktons) – Grow out of planktonic phase in some season; survival as sedentary adults; mainly found inshore; marine worms, mollusks, crabs.

What are Diatoms? • Bacillariophyta (phylum) • Unicellular protists (algae) • Cell wall impregnated with silica. • Photosynthetic (contain chlorophast) • Primary producers in oceans as well as freshwater.

What are Dinoflagellates? • Dinophyta (phylum) • Important freshwater and marine algae. • Contain chloroplast / other pigments (“red tide”) • Many possess two flagella. • Some species exhibit bioluminescence.

Red Tide due to Harmful Algal Blooms

What are Benthos? • Benthos – Bottom-dwelling organisms inhabiting floor of rivers, lakes & sea. • Mostly heterotrophic communities, detritivores/scavengers. • Two types: - Epifauna – Living on the surface or moving freely about; - Infauna – Digging/burrowing forms.

Deep Sea Benthos

Upwelling • Occurs when winds move surface waters away. • So cold water from below (rich in nutrients) comes up to the surface. • Upwelling regions have high productivity; also high fish (fisheries) and seabird biodiversity.

Upwelling In Ocean

Hydrothermal Vent in Deep Sea

Deep Sea Hydrothermal Vents • Vents and hot sulphur springs created by drifting land masses & moving tectonic plates. • Support unique communities. • Food web begins with chemosynthetic bacteria (not photosynthetic). • These fix carbon and produce organic matter by oxidizing H 2 S & other chemicals. • These bacteria are fed upon by snails/grazers. • Mutualism observed between these bacteria and tube worms.

Photosynthesis Vs. Chemosynthesis

Estuary

Estuaries and Seashores (Ecotones) • Estuary – Semi-enclosed body of water. • Freshwater from rivers is mixed with ocean water by tidal action. - e. g. coastal bay (bordered by land on 3 sides). • Salinity intermediate between salt and freshwater. • Rich in nutrients (nutrient traps). • May have high productivity, low biodiversity.

Practice Concept • On the basis of investigations, one might deduce that increased nutrient enrichment would lead to increased community diversity, which in turn would result in greater ecosystem stability. • However, Odum (1998) stated that in low-nutrient environments, an increase in community biodiversity seems to be related to an increase in productivity; • But in high-nutrient environments, an increase in primary productivity results in increased dominance of a few species, resulting in a decrease in species diversity or community richness.

Estuaries cont’d • Estuaries support communities characterized by: - Phytoplankton; - Benthic microflora: algae on rocks, sand or animal shells; - Macroflora: Large attached plants like seaweeds, marsh grasses, mangrove trees.

• Tidal action imp physical regulator in estuaries. • Adaptations to cope with tidal cycles. • e. g. Fiddler crabs have internal biological clocks; • Adjust their feeding behaviour to a favourable part of tidal cycle. If experimentally placed in a different environment, they still exhibit synchrony with tidal cycles in eating habits.

Seashore: Harbours communities similar to estuary

Mangroves • Plant communities in land-sea ecotones (estuaries) in tropics/subtropics. • Trees and shrubs adapted to harsh conditions – salty water and anaerobic mud (with low O 2 levels) halophytes. • Extensive prop roots provide surfaces for attachment of oysters and other sea animals. • Protect land from soil erosion, trap nutrients. • Efficient nursery grounds for coastal fishes. - e. g. Sunderbans in Bengal.

Mangrove

Coral Reefs (Natural Cities) • • Plant-animal superorganisms. Found in land-sea ecotones. High productivity, high diversity. Mutualism b/w coelenterates (Actinozoa) & photosynthetic algae (Zooxanthellae). • Algae supply some nutrients; animals protect. • Coelenterates secrete Ca. CO 3 skeleton. • Algae grow inside tissues of animal polyp (a column-like structure).

Coral Reef: Home to Many Fishes

Coral Reefs under Stress • Stress due to pollution/global warming. • Results in ‘bleaching’ (a survival strategy) – Algae leave the coral animal. • Finally, coral dies of starvation.

Coral-algae: An example of Obligatory Mutualism