Marine Plants

Plants in the oceans are, for the most part, very different from plants on land--like this beautiful rose we find in the sunny, terrestrial environment.

The types of plants most important in the sea is much different from those of importance on land. This is due to the difference in the environmental demands placed on plants in these two general habitats.
ference in the environmental demands placed on plants in these two general habitats.

Markedly different to the abundant diversity of animal life. The animal kingdom belongs to the sea, whereas the plant kingdom belongs to the land.

Sea water can be compared to soil water in that they both carry the nutrients necessary for plant life.

1). On land, plants have evolved extensive root systems to obtain water and food plus leaves for the uptake of carbon dioxide and the uptake/release of oxygen.

2). In the oceans, plants are completely surrounded by the nutrient-bearing sea water but have difficulty receiving enough light for photosynthesis. Thus adaptations have proceeded in the direction of being able to spend more time in the upper, sunlit waters.

Light is of prime importance to a plant and attachment to a substrate is secondary.

1). Only in a small part (less than 2%) of the oceans is there a suitable combination of sufficient light and attachment substrates. This is the zone of the upper littoral.

2). Within this 2%, large areas have unfavorable bottom for attachment to many plants. Mud, sand, shingle bottoms are not good sites.

3). Light penetrates such that at depths greater than 1 meter below the surface, only 34-38% of the light entering the surface remains. At depths greater than 50 meters, less than 1% of the light is left, with the reds and oranges totally absorbed so that blue light is all that is left.

4). Thus, the bulk of production by attached plants in the oceans is relatively insignificant and would only be able to support a small portion of the marine animals present in the vast oceanic biota.

5). The primary plant production becomes mainly a function of the phytoplankton (floating plants), notably the diatoms and dinoflagellates, which occur in incalculable numbers in the upper reaches of the world oceans.

Note: here are some words useful in the description of plants: Epiphytic=attached to another plant; epizoic=attached to an animal; lithophytic=attached to rocks.