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Lecture 32: MARINE ORGANISMS AND ENVIRONMENTS

Powerpoint Lecture Slides

Taxonomic classification
Diversity and distribution of species
Ecological classification of organisms
Marine environmental zones

Taxonomic classification - - reflects evolutionary relationships.
Kingdom
Phylum
Class
Order
Family
Genus
Species -- the fundamental category.
Any individual of a species possesses the essential
distinguishing characteristic of that species.
 
Five Kingdoms
1. Monera: unicellular bacteria,
photosynthesizing bacteria (blue-green algae)
2. Protista: unicellular but more complex;
planktonic algae and protozoans of the ocean
3. Fungi: plant-like, but do not photosynthesize
4. Plantae: multicellular plants
5. Animalia: multicellular animals
 
Diversity of life forms
1.5 millions species of plants and animals are known.
~5-30 million remain to be identified!
 
Distribution of species
Animals = 1,200,000 total
Land: 80% (majority are insects)
Oceans: 20%, or ~200,000
Inhabit the water column -- 10,000
Inhabit the bottom -- 190,000
Plants (including algae) = 300,000 total
Land: 96 % (dominated by flowering, higher plants)
Ocean: 4 %, or 11,000 (essentially all are planktonic algae)
Important note: Majority of marine "plants" are quite different in structure and in many functions from their terrestrial counterparts.
 
Organism-Environment Relationships
Essential strategies for all organisms:
o Obtain food
o Avoid being eaten
o Reproduce
Meeting those requirements dictates ....
... where organisms live -- habitat
... how they obtain food -- nutrition
 
Ecological (functional) classifications of marine organisms
Nutrition
(A) Autotrophic: synthesizes its own food from inorganic substances
Photosynthesizers: algae, some bacteria
Chemosynthesizers: bacteria in sediments and around
hydrothermal vents on the sea floor
(B) Heterotrophic: requires pre-formed organic matter as food
Herbivores: "grazers"
Carnivores: predators, scavengers
Detrivores: organic particles, or organic substances absorbed
on sediments
Filter-feeders: collect suspended organic sediments
Deposit-feeders: ingest sediment, metabolize organic matter
 
Habitat and Mobility ("Life Mode")
(A) Pelagic -- live in the water column
Planktonic: float or drift in surface waters
Nektonic: swimmers; move laterally and vertically
(B) Benthic -- live on the bottom
Epifauna: at the surface
Mobile -- crawl or swim
Sessile -- attached
Infauna: within the sediment -- burrowers
 
Marine Environmental Zones
Fundamental divisions:
Pelagic (water column)
Benthic (bottom)
Subdivisions based on depth:
Availability of ...
... sunlight (autotrophs)
... food (heterotrophs)
Variations in ...
... T and S (adaptability to changes)
... nature of the bottom -- rocky, muddy,etc.
(mobility and nutrition of benthos)
 
Oceanic Zones
1. Open ocean, "deep sea"
Relatively uniform water-column and bottom conditions
Pelagic
Epipelagic = Photic Zone (upper 200 m)
Deeper pelagic zones -- food very limited
Benthic (subdivisions not important)
Availability of food limits biomass
 
2. Coastal Zones . . more variable environments
Neritic
Photosynthesis at all depths
Abundant nekton and benthos
Benthic
Subtidal (sublittoral)
Intertidal (littoral)
Stressful environment--but populous
Supratidal ("splash")
 
(Detailed notes start here)

MARINE ORGANISMS AND ENVIRONMENTS

Taxonomic classifications -- relationships between organisms.

Organisms are classified into a hierarchy of taxonomic units that reflect evolutionary relationships.:

Kingdoms

Diversity of life.

"Diversity" refers to the number of species on Earth. We have identified and catalogued 1.5 million species of plants and animals. But, current estimates are that ~5-30 million species remain to be identified!

Distribution of species

Animal species (1,200,000 total). About 80% of known animal species occur on land; the majority are insects. Of the known marine animal species (20% of the total, or about 200,000), most (95%) live on the bottom; the remainder (5%) inhabit the water column.
Plant species, including algae (300,000 total). The great majority (96%) of plant species are terrestrial; land plants are dominated by flowering, higher plants (not algae). The remaining 4% of "plant" species living in the ocean are essentially all planktonic algae. You should note that the majority of marine "plants" are quite different in structure and in many functions from their terrestrial counterparts.

Essential strategies for all organisms:

o Obtain food
o Avoid being eaten
o Reproduce
Meeting those requirements dictates where organisms live and how they obtain food -- in other words, how organisms adapt to their environment. Those adaptations and general organism-environment interactions comprise the field of life sciences called Ecology.

Ecological (functional) classification of marine organisms is based broadly on the fundamental strategies of organisms in the sea -- food, survival, and reproduction.

Nutrition

Autotrophic organisms synthesize their own food from inorganic substances. The dominant mode of autotrophism is photosynthesis. In the oceans, photosynthesis is carried out almost exclusively by algae; there are some photosynthetic bacteria as well. Another mode of autotrophism is chemosynthesis. Bacteria in sediments and those living in and around hydrothermal and cold vents on the sea floor can synthesis organic matter (their own cells) by using the energy of a specific chemical reaction.

Heterotrophic organisms require pre-formed organic matter as food. There are a variety of heterotrophic modes of nutrition: Herbivores are "grazers" of algae or plants. Carnivores are predators or scavengers. Detritivores collect and eat organic particles suspended in sea water or organic substances absorbed on sediments. Filter-feeders collect suspended organic sediments. Deposit-feeders ingest sediment and extract any organic matter in the sediments. Parasites live on or within other organisms and rely on them for food in some manner.

Habitat and Mobility ("Life Mode")

Pelagic organisms live in the water column. Plankton float or drift in surface waters; some plankton have ability to migrate vertically. Nekton are swimmers; they can move vertically and laterally, and some can migrate over long distances

Benthic organisms live on the bottom. Epifauna live at the surface of the sea floor. Mobile epifauna crawl or swim over the surface. Sessile eprifauna are attached to the bottom substrate. Infauna live within the sediment; they are burrowers.

Marine Environmental Zones -- Habitats of Marine Animals and Plants.

The fundamental divisions of marine environmental zones are (1) Pelagic (the water column), and (2) Benthic (the sea floor). Subdivisions within this basic framework are based on depth, because several important ecological factors are depth-dependent:
Availability of sunlight -- plants (autotrophs)
Availability of food -- animals (heterotrophs)
Variations in temperature and salinity -- adaptability to changes
Variations in bottom substrate -- mobility and nutrition of benthos

(1) Oceanic Zones (the open ocean, i.e., the deep sea) are characterized by relatively uniform conditions in the water column and on the sea floor
(1a) Pelagic zones
(1a1) Epipelagic zone is the upper 200 m of the water column. As we have discussed, this is the depth range that sunlight can penetrate; it is also termed the photic zone. Therefore, all algae must live there in order to photosyntehsize. Because algae are the base of the marine food chain, most nekton also live in the epipelagic zone.
(1a2) Deeper pelagic zones are characterized by very limited supply of food (from the epipelagic zone). These zones are inhabited by exotic fish and invertebrates.
(1b) Benthic zones (subdivisions not important for our purposes). The limited availability of food limits the total biomass of animals living on the deep-sea floor.
(2) Coastal Zones (relatively shallow water of continental shelves) are more variable environments in both water column and on bottom.
(2a) Neritic zone. The entire water column in coastal oceans is shallow wnough to support photosynthesis. Therefore, there is abundant algal and plant production, and hence abundant nekton and benthos.
(2b) Benthic zones.
(2b1) Subtidal (sublittoral) -- below low-tide range.
(2b2) Intertidal (littoral) -- within tidal range. This zone is periodically submergent, then emergent. This is a stressful environment for organisms, but very populous because of the availability of abundant food.
(2b3) Supratidal ("splash") -- above high-tide range, occasionally inundated by waves.

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