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UTILITY OF SPLENIC MACROPHAGE AGGREGATES AS AN INDICATOR OF FISH EXPOSURE TO DEGRADED ENVIRONMENTS
Citation:
Fournie, J W., J K. Summers, L A. Courtney, V D. Engle, AND V. S. Blazer. UTILITY OF SPLENIC MACROPHAGE AGGREGATES AS AN INDICATOR OF FISH EXPOSURE TO DEGRADED ENVIRONMENTS. JOURNAL OF AQUATIC ANIMAL HEALTH 13(2):105-116, (2001).
Description:
The utility of splenic macrophage aggregates (MAs) as an indicator of fish exposure to degraded environments was evaluated in several species of estuarine fishes as part of the Environmental Protection Agency's Environmental Monitoring and Assessment Program - Estuaries (EMAP-E). Using image analysis, the number and mean size of MAs/mm2 were measured on tissue sections of spleen from a total of 983 fishes representing 7 species from 266 stations scattered across the Gulf of Mexico coastal estuaries. These samples were analyzed for MAs and at 16 stations at least one fish exhibited high densities (>40 MAs/mm2). Densities of MAs that exceeded 40/mm2 correlated with exposure to either hypoxic conditions or sediment contamination. Fisher's exact test showed observed frequencies of joint occurrence between high numbers of MAs and both high sediment contaminants and low dissolved oxygen were higher than the expected background frequencies. For all 16 sites where MAs >40/mm2, sediments displayed at least one contaminant at a concentration in the highest 5% of those observed for all Gulf of Mexico stations. This study demonstrates that splenic MAs are effective biotic indicators that can be used to discriminate between fish exposed to degraded and non-degraded environments.