Transcript Ecology (BIO C322)

Ecology (BIO C322)
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, Arctic, 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
and 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 H2S & 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 O2
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)
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•
•
•
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 CaCO3 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