Coastal Marine Environment Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 267

sea plants that need sunlight. Decay of algae by bacteria removes large amounts of oxygen
from the water, and may kill living organisms. Oxygen deiciency will cause sediments
to change from an aerobic to an anaerobic state. When this occurs, sulides such as pyrite,
can be formed (Fukue et al., 2003). Hydrogen sulide is a hazardous substance for ish. The
combination of oxygen depletion with hydrogen sulide makes the seawater look blue or
greenish-blue—a condition sometimes called blue tide .
Accelerated production of phytoplankton algae will lead to algae bloom—an overpop-
ulation of certain types of algae that are readily distinguished on the water surface as
patches of bloom because of their high population density. The red algae bloom known as
red tide is a vivid demonstration of such an occurrence involving certain types of algae that
contain red pigment. Some, but not all, of the red algae species are toxic. The prominent
ones are the dinolagellate Alexandrium tamarense and the diatom Pseudo-nitzschia australis
(WHOI, 2014) . Their production of neurotoxins makes them harmful to ish and other
aquatic life forms—and even humans. Remediation treatment is needed if one wishes to
maintain a healthy environment in the coastal marine ecosystem to counter the effects of
the preceding.
Many countries, states, and communities have set up programs for monitoring of surface
water quality. The term surface water is used here in the overall deining sense to mean all
water that is naturally exposed to the atmosphere. This includes rivers, lakes, reservoirs,
ponds, streams, impoundments, seas, estuaries, and all springs, wells, or other collectors
directly connected to surface water. In general, the quality of surface water has a direct
inluence on its sediments, benthic organisms and plankton. Data obtained on surface
water quality are used to structure measures to counter eutrophication and contamination
of surface water.
8.2.4 Food Chain and Biological Concentration
Some organic matter, such as phytoplankton, deposited onto the sea bottom or suspended
in seawater will be decomposed by microorganisms or will be consumed by small ben-
thic animals called zooplankton. Phytoplankton is the irst level in the marine food chain
and zooplankton are the second trophic level. Decomposition of the phytoplankton and
other organic matter will produce detritus. This is a good source of nutrients. The food
chain starting from detritus is often called the detritus food chain , in contrast to the food
chain starting from phytoplankton in seawater. These food chains are the most important
process for the preservation of marine environment and living organisms such as ish,
shellish, sea plants, etc. These are important sources of protein and minerals for humans.
However, the food source for these marine living organisms can contain toxic and hazard-
ous substances bioaccumulated through uptake, for example, through the gills of ishes.
Bioaccumulation refers to the uptake and storage of a contaminant—generally, a toxic
substance—by an organism in the food chain. Bioaccumulation in ish presents health
problems to humans when these are ingested. Although uptake of a toxic substance is an
important measure, we need to account for possible excretion of the substance and also met-
abolic transformation of the substance as factors that will reduce the uptake amount of the
substance. Hence, storage becomes an important consideration. The literature shows that
the term bioconcentration is quite often used in place of bioaccumulation. Bioconcentration
is related to bioaccumulation, but is more speciic in that it expressly refers to the uptake
and storage of toxic substances from water. The term bioconcentration has also been used
to indicate the condition when concentrations of a substance in a particular biota are higher
than in the surrounding medium. For this discussion, we use the irst meaning of the term