Page 24 - Professorial Lecture - Prof Omoregie

Chemical accumulation and toxicity depend not just on the total chemical
concentration in the environment, but also on how readily the fish can absorb
these different chemicals through the gills, across the skin and within the
digestive tract.

EFFECTS OF POLLUTANTS ON MARINE PRODUCTIVITY AND FISHERIES

Productivity module indicators

Primary productivity can be related to the carrying capacity of an ecosystem for
supporting fish resources (Pauly & Christensen 1995). Measurements of
ecosystem productivity can be useful indicators of the growing problem of
eutrophication. In several LMEs, excessive nutrient loadings to coastal waters
have been related to the following:
1. Algal blooms implicated in mass mortalities of living resources,
2. Emergence of pathogens (e.g. paralytic shellfish toxins),
3. Explosive growth of non-indigenous species (Epstein 1993, Sherman
2000).

The ecosystem parameters measured and used as indicators of changing
conditions in the productivity module are zooplankton biodiversity and species
composition, zooplankton biomass, water-column structure, photosynthetically
active radiation, transparency, chlorophyll-a, nitrite, nitrate, and primary
production, (Aiken 1999, Berman & Sherman 2001, Melrose et al. 2006).
 The productivity of many marine systems is limited by nutrient
availability, and the input of additional nutrients to these systems
increase primary productivity.
 In the moderation of some systems, nutrient enrichment can have
beneficial impacts such as increasing fish production; however, more
generally the consequences of nutrient enrichment for coastal marine
ecosystems are detrimental. Many of these detrimental consequences
are associated with eutrophication.
 The increased productivity from eutrophication increases oxygen
consumption in the system and can lead to low-oxygen (hypoxic) or
oxygen-free (anoxic) water bodies. This can lead to fish kills as well as
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