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International Journal of Marine Science 2014, Vol.4, No.42, 1-11
http://ijms.biopublisher.ca
2
are of great ecological importance since they
contribute considerably to primary productivity
available to both the benthic and the pelagic community.
In addition to supplying food resources, microalgae
excrete high molecular weight polysaccharides that
contribute to sediment stabilization and reduce
sediment resuspension during both tidal emergence
and storms (Herman et al. 1999).
Chlorophyll is a reliable index of microalgae biomass.
Chlorophyll
a
pigments have proven useful in
explaining localized patterns of biodiversity (Pinckey
et al., 1994). Primary production can be estimated
from analysis of chl-a in surface waters (Daemen,
1986; Cole and Cloern, 1987). The Chlorin Index (CI)
(Schubert et al. 2005) which is a measure of the
amount of chlorophyll and its degradation products
that could be transformed to phaeophytin, has been
used as a geochemical surrogate of biodiversity.
Chlorophyll content is a measure of phytoplankton
and microphytobenthos (MPB) biomass which are the
main primary producers in estuarine environment
(MacIntyre and Cullen, 1995). The productivity of
benthic algae is dependent on various environmental
variables such as availability of light, emersion
periods during tidal cycle, etc. Various researches on
estimation of benthic algal biomass in estuarine and
mud flats have been carried out in the past
(Underwood and Kromkamp, 1999; Murphy
et al
.,
2008), and in most of the studies, the biomass of MPB
is often expressed as chl-a, which is widely distributed
and the most abundant pigment component in most
species of microalgae hence is used to estimate
micoalgal biomass (Sun et al., 1994). Benthic
microalgae are known to be extremely variable and
exhibit spatial and temporal heterogeneity (Platt et al.,
1980). In sediments and water column, chlorophyll
content is reported to vary both horizontally and
vertically (Colijn and de Jonge, 1984; Pinckney and
Sandulli, 1990; Buffan-Dubau and Carman, 2000;
Murphy et al., 2008).
Macroinvertebrates are important part of the aquatic
food chain. Benthic invertebrates play important roles
in transitional ecosystems, by filtering phytoplankton
and then acting as a food source for larger organisms
such as fish, thereby linking primary production with
higher trophic levels. These macoinvertebrates acquire
their food in a variety of ways. The general behavioral
mechanisms of food acquisition in different species
can result in the ingestion of a wide range of food
items (Merritt
et al
., 1996). Scrapers (grazers),
consume algae and associated material; shredders,
consume leaf litter or other coarse particulate organic
matter (CPOM), including wood; collectors
(gatherers), collect fine particulate organic matter
(FPOM) from the stream bottom; filterers, collect
FPOM from the water column using a variety of filters;
and predators, feed on other consumers. The deposit
feeders include those that selectively feed on the
surface deposits and those that ingest surface and
subsurface deposits indiscriminately.
The food supply of the benthic macroinvertebrates
directly or indirectly, depend almost entirely from
living and dead particulate matter sinking from the
overlying water (Dudley et al. 1986; Herman et al.
1999). Microalgae in the surface water and sediment
form a primary food source which supports many
benthic macroinvertebrates. Detrital matter derived
from primary productivity also constitute a valuable
resource for benthic macroinvertebrtaes and make up
the only energy input to the aphotic zone (Middlelburg
et al
. 1996; Herman et al. 1999; Kendrick
et al
. 1998;
Kang et al., 2003). It is generally accepted that the
flux of particulate organic carbon (POC) from the
euphotic zone controls the biomass and abundance of
deep-sea benthos.
Benthic communities play a critical role in the
functioning of estuaries. Chlorophyll composition and
benthic consumers are essential components of coastal
ecosystems (MacIntyre et al., 1996) influencing
sediment biogeochemistry via uptake and release of
nutrients (Kang et al. 2003), and sediment erosion via
their production of exopolymers (Pinckney et al.,
1994), hence an attempt to establishing the relationship
between them is worth an ecological adventure.
Very little is known about the distribution of
chlorophyll in the Nigerian aquatic system, and
apparently no attempt has been made to relate primary
production to the abundance and diversity of benthic
macroinvertebrates. The main objective of this present
paper is to determine whether primary productivity
expressed as concentration of chl-a in sediment and
surface water directly affects the abundance and
diversity of benthic macroinvertebrates. This will