Unit 4 Benthos Marine Ecology Notes

Epifauna

Organisms that live on or above the substrate

Infauna

Organisms that live in the substrate

Macrofauna, meiofauna, and microfauna

Infauna are divided into categories based on size...

Macrofauna

Greater than 0.5 mm

Meiofauna

0.5 mm to 0.062 mm

Microfauna

Smaller than 0.062 mm

Phylum Echinodermata

Contains over 6,000 species including sea stars, sea urchins and sea cucumbers

Echinodermata characteristics

Have radial symmetry and a water vascular system, most are planktonic with bilateral symmetry.

Phylum Cnidaria

Includes corals, anemones, jellyfish, and hydroids. With about 9,000 species it is very diverse

Cnidocytes

Stinging cells

Harpoon-like nematocyst

Injects toxins into the victim

Mollusks

Over 50,000 species including gastropods (snails & sea slugs), bivalves (clams, scallops, oysters etc.), and cephalopods (octopuses, squid, cuttlefish & nautilus)

Characteristics of Mollusks

Well-developed body organs but lack body segmentation

Arthropoda

The largest phylum of life on Earth. Over 1 million species, with the vast majority being insects.

Crustaceans

Most marine arthropods are

Characteristics of crustaceans

Have an exoskeleton and most have five pairs of appendages, often with claws

By analyzing the benthic macroinvertebrate population

The health of a freshwater and estuarine system is often measured by

Stream index

Can be calculated based on the relative abundance of different species

Sedimentary communities

Sandy, unstable substrate

Sediment destabilizers & sediment stabilizers

Benthic organisms in the sedimentary subtidal zone may be classified into these two major groups

Bioturbators

Sediment Destabilizers are otherwise known as

Sediment destabilizers

Include both mobile and sedentary organisms that cause sediment to move and become resuspended

Sediment stabilizers

Include various seagreasses whose roots bind sediments and frequently restrict burrowing animals (competitive interference)

Surface predators

These animals are xposed at the surface and take organisms at or near the surface without disrupting the sediment structure

Burrowing predators

These animals move down various tubes or channels provided by the deep-dwelling prey and attack them

Infaunal predators

These animals burrow through sediment and live in it at all times

Rocky subtidal communities

Not as common as sedimentary communities, have a hard substrate with low-growing encrusting plants and animals

colder temperate regions

Where are the hard subtidal substrates dominated by very large brown algae (kelp)

Kelp

Very large brown algae

Kelp beds

When the algae does not form a surface canopy

Kelp forest

When the algae forms a floating canopy

Holdfast

Instead of true roots, what are kelp attached to the substrate by?

Stipe

Arises from the holdfast, stem-like/trunk-like, ends in one or more broad, flat blade

Pneumatocyst

Float, at the base of the blade, keeps the blade at the surface

Seagrasses

Flowering plants adapted to live submerged in seawater

Soft substrate

Although all types of substrates are inhabited by seaagrasses, where does the most extensive bed occur?

Depositional environments

Seagrass beds are ____, often with high organic content that can make the sediment under the bed anaerobic

Interstitial organisms

Otherwise known as Meiofauna, these organisms occupy the microspaces between particles or live in individual particles

Grain size

Most important factor determining the presence, absence, and types of meiofauna

the greater the size and number of meiofauna

The coarser the grain size, the greater the volume of interstitial space, and therefore....

Temperature

Limiting factor: the most extreme range occurs in intertidal beaches and minimally in subtidal sediments

Salinity

Limiting factor: Particularly in intertidal areas where freshwater runoff occurs

Wave Action

Limiting Factor: Both intertidally and subtidally affecting the arrangement of sediment

Statocyst

Major adaptation of most meiofauna, an organ that detects gravity and helps the organism differentiate up and down

simpler anatomy

Reduction in cell number

elongated, wormlike

Vermiform shape

Neoteny

retention of larval form

Haptic

Ability to cling to grains by an adhesive material or hooks and claws

Efficient reproduction

short life cycle, few gametes

Sponges

Porifera

Cnidaria

Coral, sea anemones, siphonophones

Platyhelminthes

Flatworms, flukes, tapeworms

Nematoda

Roundworms

Annelida

segmented worms

Mollusca

Chitons, snails, bivalves

Arthropod

Crabs, shrimp, barnacles

Echinodermata

Sea stars, sea urchins, sea cucmbers

Chordata

Fish, tunicates