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Introduction to Marine Ecology

I. Shoreline habitats

A. Shoreline zonation (Fig. 8-4)

1. Intratidal (littoral) – between the tides, periodically submerged and uncovered

2. Supratidal – above high tide

3. Subtidal – below low tide

B. High wave action habitats

1. Sandy beach

2. Rocky intertidal

3. Tide pool

C. Low wave action habitats

1. Mud flat

2. Salt marsh

3. Sea grass bed

II. Distribution of marine life

A. Pelagic organisms

1. Plankton
   a. Phytoplankton
   b. Zooplankton

2. Nekton – cephalopds, fish, reptiles, birds, mammals

B. Benthic organisms (Fig. 8-5)

1. Demersal – capable of swimming, hang on bottom sometimes

2. Epifauna – live ON substrate
   a. sessile - barnacle
   b. motile - crab

3. Infauna – live IN substrate, clams

III. Factors effecting community structure in marine habitats

A. Bottom-up regulation - control of the diversity & abundance of species in the community based on the level of primary production.

1. Primary production - Without primary production, food webs would collapse

2. Seasonality of primary production blooms is often followed by increased pop size of other species. (FIG)

B. Top-down regulation - control of the diversity & abundance of species in the community based on the presence of consumers.
- e.g. Wave exposed shorelines - starfish & predatory snails keep mussels & barnacles in check
-e.g. In soft-substrate habitats crabs & fish keep benthic inverts in check.

1. Keystone predator - has the greatest effect on community diversity if removed (limits the growth of the best competitor).

2. Direct effect of consumer - can limit potentially abundant prey to refuge habitats, where their growth is restricted
   e.g. mussels to the intertidal zone where starfish cannot go, urchins to under rocks etc.
   Sea otters on urchins

3. Indirect effects of consumer - includes several mechanisms including:
   a. Habitat modification - by altering a given habitat, the # and abundance of other species is effects
   Urchins eat kelp, so species that would live in/on the kelp cannot exits here.
   b. Trophic cascades - by eating a given species, the predator is allowing greater growth of the competitors and prey of that species
   Fish eats grass shrimp, anemones flourish
   Gulls or sea gulls eat urchins, algae flourishes

4. If keystone predator is removed - dominant competitor can ravage ecosystem & cause biodiversity to drop

C. Competition - essential in determining the make-up of communities, particularly the high and species dominance of vertical zonation.

1. Exploitative competition - decreasing resource availability (multiple filter feeders in one area clearing the water)

2. Preemptive competition - using up a resource before a competitor has the opportunity to do so - space (barnacles settling on rock and beginning to grow before the water in warm enough for the algae to attach & grow)

3. Interference competition - physical conflict over a resource (two species of coral fighting over space, two scavengers fighting over a carcass)

IV. Consumer feeding strategies

A. Suspension feeders - filter plankton out of the water column, convert pelagic biomass to benthic biomass

1. Active - filter feeding water moved or limbs swept through water - barnacles clams, etc.

2. Passive suspension feeding - movement except that of the water - tube worms, etc

B. Deposit feeders - ingest & process sediments, removing & digesting organic material - marine worms, fiddler crabs, sand dollar

C. Herbivores - graze on algae (surface algae or leaf algae)
snails - use radula
sea urchins - use Aristotle's lantern

D. Predators - feed on other non-plant species
snails, crabs, starfish, fish, birds, mammals

E. Scavengers - feed on anything dead
as above

F. Photosynthetic - many marine animals harbor photosynthetic symbitotic zooxanthellae
giant clam, anemones, urchins, corals, etc.

V. Brief introduction to marine zoology (as introduced in Martinez)

A. Algae

B. Sponges

C. Cnidarians

D. Ctenophora

E. Bryozoans

F. Brachiopoda

G. Molluscs

H. Annelids

I. Arthropods

J. Echinderms

K. Chordates

1. Tunicates

2. Vertebrates

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