The Lagos lagoon is a coastal lagoon and hence, is highly impacted by pollutants
from anthropogenic sources. The greater percentage of these pollutants is organic in origin.
Hydrochemistry and benthic fauna assemblage of five anthropogenically impacted sites of the
Lagos lagoon, Nigeria were studied from May to October, 2016 to investigate the effects of
organic pollution on them. Water and composite benthic samples were collected monthly at
each study station and analysed in the laboratory following standard procedures. The analysis of
variance (ANOVA) indicated no significant difference (p > 0.05) in values of the water
parameters measured among the study stations. Higher pH values were recorded at Carter
Bridge sampling station and this could be attributed the introduction of carbonates into the water
through the washing of cement bags. Salinity of the water was generally low due to the season
of the sampling. Introduction of large volumes of biodegradable wastes both reduced the
dissolved oxygen level and increased the total suspended solids in the waters of critical sites. A
total of 243 benthic macrofauna individuals comprising three Phyla, four Classes, four Orders,
eight Families, eight Genera and eight Species were sampled. The gastropods,
Pachymelania aurita
and
Tympanotonus fuscatus
dominated the benthic macrofauna assemblage of the study
area accounting for 40.3% and 19.3% respectively. The relatively low abundance of the filterfeeding
bivalves and the highly sensitive arthropod species in the study area may be indicative
of organic pollution of the area.
