Marine ecology: Understanding the distribution and abundance of marine organisms

How do organisms relate to their environment?

How do various ecological and evolutionary factors promote and maintain marine biodiversity?

First, some review

Where do ecologists focus to seek pattern?

Individuals

Populations

Communities

Ecosystems

Remember how populations grow

How does the bipartite life history of marine organisms contribute to population dynamics?

Thinking about ecological interactions:

Competition

Predation

Symbiotic associations

 

The flow of energy and materials within marine habitats

Ultimately, patterns of distribution and abundance are influenced by spatial and temporal patterns of energy availability and how organisms within populations obtain that energy for reproduction, growth, and survival.

Where does energy come from and where does it go?

Virtually all biological energy is ultimately derived from solar radiation via photosynthesis... however the lack of critical nutrients can limit rates of productivity.

Some definitions:

Productivity is the amount of living tissue produced during some unit of time

This is generally estimated in terms of carbon production.

Oceanographers often consider the amount of carbon (C) produced within a square meter of sea surface: i.e., g C/m²/day

Biomass is the total amount of living material found in a particular area at any given time (e.g. g C/m²)... as such it is a density... this is related to the standing crop, which is often a measure of the number of individuals within a given area

Trophic Level describes a group of organisms (species) that consume the same things (species).

Food webs describe the specific sequence of "who eats who" in terms of energy transfer within a community.

A Food Chain is the path that energy follows through a series of ascending trophic levels

Food chain efficiency is the amount of energy transferred from a lower trophic level to a higher one.

 

The importance of distinguishing between productivity and standing crop (often substituted for biomass).

 

Patterns of energy transfer between and within trophic level identify the relative importance of predation and competition within communities.

Most energy is not transferred between tropic levels (~ 10- 15 % is a typical level of energy transfer for ectotherms in the marine realm)

Levels of primary productivity establish the potential abundance of organisms at higher trophic levels.

Thus, under stable conditions, predators are generally much less common than their prey

Higher levels of productivity typically relate inversely with food web complexity... this relates to levels of environmental stability and the presence of resource niches in space or time.

Geographic patterns:

High levels of primary productivity occur along wind-swept coastal margins (100-200 m depth) and other areas of upwelling.

These shallower areas allow nutrients not consumed initially to be re-suspended.

When water masses converge in the open ocean, nutrients can become concentrated, increasing primary productivity.

Central oceans and gyre centers are nutrient poor.

Estimating Primary Productivity:

Oxygen production correlates positively with photosynthetic rate, however, a simple "snap shot" of oxygen levels may not reflect oxygen production

Changes in the ratio of Radioactively labeled carbon (experimental added to a sample) can indicate the rates of carbon uptake.

Reflectance of certain wavelengths of light (usually red) roughly indicates phytoplankton concentrations (usually done with satellites).

Photosynthetic activity can also be estimated by the fluorescence of samples exposed to a series of light flashes.