Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 3 Environmental Baseline
3.4. BIOLOGICAL CONTAMINANTS
Exposure of marine organisms to contaminants can occur either through uptake of dissolved fractions
across the gills or skin or direct digestion of the pollutant. Organisms spending the majority of their
life‐cycle in the water column are likely to receive highest exposure to contaminants that remain in
solution though some will also accumulate sediment bound contaminants indirectly through their diet
(i.e. digestion of animals that have accumulated the contaminants in their tissues). Organisms
associated with the seabed (benthic organisms) are more exposed to particle bound contaminants
with the main exposure route being either directly through ingestion of contaminated sediments or
through their diet. Benthic organisms can also absorb contaminants through the surface membranes
as a result of contact with interstitial water.
Elevated levels of contaminants can affect organisms (flora and fauna) in a variety of ways (UK Marine
SACs Project, 2001) ranging from cellular or organellular effects in individuals to ecosystem effects
resulting from changes in population sizes or even the loss of an entire species.
The incorporation of even minimal quantities of hydrocarbons in the tissue of a marine organism can
affect its predators. At every link in the food chain, organisms consume around 10 kg of matter from
the level below to produce 1 kg of their own living matter. If a contaminant passes from one level to
another without being broken down, its concentration in the living matter multiplies nearly ten times
at each link in the chain. Organisms at the top of the food chain can therefore be exposed to
detrimentally high concentrations of a product which will not affect the organisms further down the
chain. This is the phenomenon of bioaccumulation of chemicals through the food chain. Fortunately
many of the components of oil and petroleum products are biodegradable at some level of the food
chain. Of the hydrocarbons only the rarer, higher molecular weight PAHs tend to have a significant
bioaccumulation potential. The primary risk from these PAHs is that some are carcinogenic with the
impacts including acute toxicity, liver neoplasm and other abnormalities.
PCBs are usually found in the sediment rather than the water column as they tend to absorb to
particulate matter and have a relatively low water solubility. They have been identified as endocrine
disruptors and have been shown to be toxic to aquatic organisms at a range of concentrations
between 12 µg/l to 10 mg/l, however the main concern with PCBs is their potential to bioaccumulate.
As with PAHs and PCBs the consequences associated with elevated heavy metal concentrations are to
both aquatic organisms and humans as a result of consuming contaminated fish and shellfish
(MPMMG, 1998). Depending on the metal and level of bioaccumulation the effects in animals can be
as severe as anemia, renal failure and cancer.
3.5. MARINE FLORA AND FAUNA
Typical of a shallow region in a temperate climatic zone, the North Sea is a complex and productive
ecosystem which supports important fish, seabird and marine mammal populations. Pelagic and
benthic communities are interlinked in more or less tightly coupled food webs which together with
the abiotic environment, make up marine ecosystems. The flora and fauna that interact to make up
the North Sea ecosystem are discussed below.
3.5.1. PLANKTON
Plankton are drifting organisms that inhabit the pelagic zone of a body of water and include single
celled organisms such as bacteria as well as plants (phytoplankton) and animals (zooplankton).
Phytoplankton are the primary producers of organic matter in the marine environment and form the
basis of marine ecosystem food chains. They are grazed on by zooplankton and larger species such as
fish, birds and cetaceans. Therefore, the distribution of plankton directly influences the movement
and distribution of other marine species. Plankton also includes the eggs, larvae and spores of non‐
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