Climate and Biodiversity - Environmental Science - page 97

A more accurate name for the earth would be Ocean —
after all, saltwater oceans cover about 71% of the
planet's surface (Figure 5-24). They contain about
250,000 known species of marine plants and animals
and provide many important ecological and economic
services (Figure 5-25).
As landlubbers, humans have a distorted and lim-
ited view of our watery home planet. We know more
about the surface of the moon than about the oceans
that cover most of the earth. According to aquatic sci-
entists, the greatly increased scientific investigation of
poorly understood marine and freshwater aquatic sys-
tems could yield immense ecological and economic
benefits.

Natural Capital

Marine Ecosystems

Ecological
Services

Economic
Services

Climate
moderation

Food

CO 2 absorption Animal and pet

feed (fish meal)

Nutrient cycling

Waste treatment
and dilution

Pharmaceuticals

Reduced storm
impact
(mangrove,
barrier islands,
coastal
wetlands)

Harbors and
transportation
routes

The Coastal Zone: Where Most
of the Action Is
The coastal zone accounts for less than 10% of the
world's ocean area but contains 90% of all marine
species.
Oceans have two major life zones: the coastal zone and
the open sea (Figure 5-26, p. 98). The coastal zone is
the warm, nutrient-rich, shallow water that extends
from the high-tide mark on land to the gently sloping,
shallow edge of the continental shelf (the submerged
part of the continents). This zone has numerous inter-
actions with the land, so human activities readily
affect it.
Although it makes up less than 10% of the world's
ocean area, the coastal zone contains 90% of all marine
species and is the site of most large commercial marine
fisheries. Most ecosystems found in the coastal zone
have a very high NPP per unit of area, thanks to the
zone's ample supplies of sunlight and plant nutrients
that flow from land and are distributed by wind and
ocean currents.

Coastal habitats
for humans

Habitats and
nursery areas for
marine and
terrestrial
species

Recreation

Employment

Offshore oil and
natural gas

Genetic
resources and
biodiversity

Minerals

Scientific
information

Building materials

Figure 5-25 Natural capital: major ecological and economic
services provided by marine systems.

Learn about ocean provinces where all ocean life exists at
Environmental ScienceNow.

Estuaries, Coastal Wetlands, and Mangrove
Swamps: Centers of Productivity
Several highly productive coastal ecosystems face
increasing stress from human activities.
One highly productive area in the coastal zone is an es-
tuary, a partially enclosed area of coastal water where
seawater mixes with fresh water and nutrients from
rivers, streams, and runoff from land (Figure 5-27,
p. 98). Estuaries and their associated coastal wetlands
(land areas covered with water all or part of the year)
include river mouths, inlets, bays, sounds, mangrove
forest swamps in tropical waters, and salt marshes in
temperate zones (Figure 5-28, p. 99).
The constant water movement stirs up the
nutrient-rich silt, making it available to producers. For

Ocean hemisphere Land-ocean hemisphere

Figure 5-24 Natural capital: the ocean planet. The salty
oceans cover 71% of the earth's surface. About 97% of the
earth's water is in the interconnected oceans, which cover 90%
of the planet's mostly ocean hemisphere (left) and 50% of its
land-ocean hemisphere (right). Freshwater systems cover less
than 1% of the earth's surface.