Aquatic Biodiversity

Nonindigenous speciesThreatened and endangered

species

Outline

Determinants of community structure

Measuring biodiversity High diverse ecosystems Role of introduced species Extinctions and threatened species

What is community structure? Different sites have different

compositions of species If communities have structure, then

they must be more than a group of randomly selected individuals of different species

Is it random? Or is it not? What evidence do we have?

Species pool

Assessing Community Structure

Species Pool What determines this?

Species Richness What determines this?

Evenness

Measuring Diversity Shannon-Weaver

Index S=total number of

species Pj is proportion of

total population that is species j

Evenness E=H’/lnS

Types of diversity

α diversity: within-habitat

β diversity: between-habitat

Effects of sample size and drainage basin

Effect of latitude

Predatory Gastropods

A) molluscs B) fish

Diverse Aquatic Ecosystems African rift lakes

Lakes Tanganyika and Malawi – cichlid species look similar but are genetically dissimilar

Introduced aquatic species

Biotic groups How many species? Examples?

How did they get introduced? What is being done to control them?

Introduced aquatic species

The problem is getting BIGGER

Where do they come from?

How do they get here?

Brook trout

Stocked for sportfishing since the 1800sArizona in 1920 Missouri from 1879 to 1914

Round Goby

Introduced to Great Lakes in 1990svia freighter ballast

Has undergone population explosion

Grass carp Stocked for biological control of vegetation. First imported in 1963 to aquaculture facilities in

Alabama and Arkansas. The first release into open waters took place in

Arkansas, when fish escaped the Fish Farming Experimental Station

Spread rapidly widely scattered research projects stockings by federal, state, and local government agencies legal and illegal interstate transport and release by

individuals, etc. Stocking of grass carp as a biological control against

nuisance aquatic plants in ponds and lakes continues. thousands of grass carp are reared and sold by fish

farmers in Missouri and Arkansas

Grass Carp indirect effects better growth of rainbow trout due to increases in phytoplankton

and zooplankton production also higher predation on rainbow trout by cormorants due to

lack of cover, and changes in diet, densities, and growth of native fishes.

Increases in phytoplankton populations is a secondary effect A single grass carp can digest only about half of the

approximately 45 kg of plant material that it consumes each day. Nondigested material causes algal blooms, which can reduce water clarity and decrease oxygen levels (Bain 1993).

may carry several parasites and diseases known to be transmissible to native fishes

Asian tapeworm; thus responsible indirectly for the infection of the endangered woundfin

Triploid grass carp Considered to be sterile and incapable of

reproduction some researchers have questioned the sterility

of triploids can produce some viable gametes, but the

proportion of such gametes is extremely low Nevertheless, techniques used to induce triploidy are not always totally effective and every

Triploid grass carp are indistinguishable in external morphology from normal (fertile) diploids