Marine Ecology
Classification of organisms
Basic Ecology

Kelp Ecology

Due to commercial whaling Grey whale numbers decreased in the North Pacific. The resident population of Killer Whales who preyed on the Grey Whales, first turned their attention to Sea Lions but once they had devastated their numbers switched to hunting Sea Otters.

As Sea Otters are much smaller than sea Lions or Whales the Killer Whales had to eat a large number of them to survive. So the Sea Otter numbers plummeted.

Sea Otters primary food source are Sea Urchins which in turn eat Kelp. So while Sea Otter numbers decreased, Sea Urchin numbers increased and the Kelp forests disappeared due to increased Sea Urchin preditation.

Kelp forests are a primary breading ground for fish. So once the proctection of the Kelp was removed local fish numbers dropped causing a crash in the Cod market which it has still not recovered from.

It has been stated that the commercial whaling was carried out to reduced Grey Whale numbers who were being blamed for reduced fish stocks by local fisherman.

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Marine Ecology

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Introduction

Ecology is the study of the inter-relationships between the physical and biological aspects of the environment. It is the study of how organisms adapt to their environment and in turn alter it. The factors that characterize ocean environments are many, including temperature, salinity,water pressure, dissolved gases, nutrients, light levels and many more. Changing any one of these can have an unforeseen effects within an ecosystem, destroying food chains in the process. See kelp ecology in side bar.

Life in the ocean is extremely diverse and unevenly distributed both on the bottom and within the water column. Most of this biological richness is not even apparent, because many of the planets and animals are microscopic and can only be seen under a microscope. The oceans consist of an astounding variety of habitats populated by a bewildering assortment of organisms.

Ocean Habitats

Ocean habitats can first be broken down into 2 groups, the benthonic province (sea bottom) and the pelagic province,from the water column. Thus separating organisms into bottom dwellers and those that dwell in the water such as fish. Each of these areas can then be subdivided into different zones depending on their depth or in some cases the amount of light they receive.

There are two major marine provinces: the benthonic (bottom) and the pelagic (water column).

The benthonic environment is divided by depth into the:
   Littoral zone                  Inter tidal zone
   Sublittoral zone,                 0 to 200m     (continental shelf)
   Bathyal zone,                 200 to 2000m    (shelf wall)
   Abyssal zone,              2000 to 6000m    (abyssal plains)
   and the Hadal zone.              > 6000m    (deep sea trenches)
The pelagic environment is divided into the:

Neritic Zone (water over the continental shelf, no sub divisions)
and the
Oceanic Zone. (water beyond the shelf break, deep ocean water)

because of the range in depths, the oceanic zone is subdivided further into the:

Epipelagic 0 to 200m
Mesopelagic 200 to 1000m
Bathypalagic 1000m to 2000m
Abyssalpelagic 2000m to 6000m
Hadelpelagic > 6000m

The oceanic zone can also be divided into different zones based upon depth of light penetration.

The photic zone is the depth where light is sufficient for photosynthesis during the day. ( 0 to 100m)
The dysphotic zone (twilight zone) is where illumination is too weak for photosynthesis. (100 to 450m approx)
The aphotic zone receives no light from the surface because it is all absorbed by the water above. ( > 450m)

Diagram showing different habitat zones within the Earth's oceans.

ocean zones depths

Now we have some understanding of marine environments we can move onto considering the classification of organisms within the different habitats. Classification of organisms.