Key Ideas about the Sea's Surface
- The skin of the sea is only centimetres thick, but because
it covers 71% of the surface of the planet, it is the largest
single ecosystem.
- The upper meter of seawater is divided in to sublayers, each
with its own biological and chemical features. Within the surface
layer, (the upper 60 centimetres), the first 0.05 millimetres
contains an especially dense concentration of minerals, organic
chemicals, protozoans and micro-organisms. The upper 70 millimetres
has dense concentrations of slightly larger organisms, including
fish eggs, fish larvae, and crustaceans. Larger, floating jellyfish
and seaweeds are found in the upper 30 centimetres. Plus, there
are many transient creatures that move up and down in tune to
the sunlight.
- Some animals live their whole lives on the surface of the
sea. These creatures are known as neuston, and include
such things as the blue-bottle stinger, and many microscopic plants
and animals.
- A large number of sea creatures spend the most sensitive times
of their lives at the surface of the sea. Eggs of many species
of fish and invertebrates are shed into the sea by their parents.
These eggs contain fats, so they float to the surface. There,
they develop into tiny swimming creatures called larvae
and move deeper into the water. But for a few hours or days, they
inhabit the skin of the sea, and may return to this layer to feed
as they grow older.
- Eggs and the very young stages of life are very fragile and
sensitive to environmental poisons. Dr. Hardy discovered that
fish eggs that develop where the surface of the sea is polluted
either die, develop slowly, or become malformed.
- The plants and animals that live in the water excrete many
organic compounds, such as amino acids, proteins, and fatty acids
that serve as nutrients for bacterial growth. These rise to the
surface where they are concentrated the thin organic skin of the
water. This happens in fresh water as well as salt water.
- When water creatures - from microscopic to large - die, the
oils in their bodies may float to the surface before they completely
decompose.
- The thin layer of oily material on the surface of the sea
is an important part of the water cycle as it helps control the
rate of evaporation. It is also a highly nutritious food source
for many species of microscopic plants and animals called Plankton.
On calm days we say the sea is "slick calm" or "oily
calm" because the microscopic layer of oil is evenly distributed
on the surface.
- Wind pushes the oil into long ribbons of calm water known
as "wind slicks" or "wind rows." You
can see these on most days when looking at the sea from an overlook
or from a boat. Samples show the plankton and nutrients are many
thousands of times more concentrated in the windrows than in water
only a few centimetres deeper or in adjacent areas.
- Unfortunately, the oily surface of the sea is also the first
to receive pollutants from the atmosphere. Scientists believe
more than 30 per cent of all ocean pollution comes from tiny particles
of dust and smoke in the air - often called fallout. This
settles on the most sensitive and vulnerable part of the ocean
- its skin. The pollutants contain pesticides, heavy metals, and
industrial and motor vehicle toxins such as sulphuric acid, chlorine,
and dioxin.
- Dr. Hardy says, "In the more than 200 microlayer samples
we have collected from rivers, estuaries, bays and oceans, there
is a sadly consistent picture: the surface microlayer is becoming
a soup of toxic metals, organic pollutants, bacteria, pesticide
residues, and the by-products of combustion-derived hydrocarbons
from cars, trucks, aeroplanes, refuse incinerators, and power
plants. Coastal sewage waste-water discharges, runoff from municipal
and agricultural drainage systems and direct industrial discharges
into rivers contribute to the contamination."
- "A polluted surface microlayer has the potential to poison
much of the complex marine food web, including fish, crustaceans,
whales, and seabirds. "Destruction of the microlayer may
alter the exchange of materials between the atmosphere and the
ocean, thereby affecting global climate."
- Oil pollution also floats on the
surface of the sea and quickly contaminates this fragile environment
with chemical toxins. Oil, even a very thin layer, spreading over
the surface of the water at the same time fish are releasing their
floating eggs can devastate their reproductive success.
- Dr. Hardy found heavy metals, and other toxins, are hundreds
of times more concentrated in the surface windrows of the sea
than in deeper water. He found pesticides concentrated millions
of times greater than in the rest of the water.
- As the ozone layer in the upper atmosphere breaks down from
air pollution, ultraviolet radiation increases. This has been
shown to have a severe impact on the phytoplankton and the eggs
of sea creatures when they concentrate at the surface.
- The surface of the sea is a critical habitat for most of the
world's major fish species as well as the invertebrates - like
lobsters, shrimp, oysters, clams and mussels. If the toxins are
killing these when they are eggs or when they are very young,
even a small fishing pressure could result in rapid failure of
the fishery.
