Plant Life in Soft Bottom Communities

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PLANT LIFE IN SOFT BOTTOM COMMUNITIES
1. INTRODUCTION
This paper deals with plants that are found in soft bottom communities that are either found in freshwater or marine environment. These plants are submerged therefore having different adaptation for this environment. These different adaptations were tackled in this paper as well as the physico-chemical parameters present in their environment. These plants have changes in their morphology to be able to cope with the environment. For example are leaves that are highly dissected for greater area of diffusion for carbon dioxide since CO2 concentrations in the water column are very minimal. These plants provide ecosystem services that rank among the highest of all ecosystems on earth. The direct monetary outputs are substantial since highly valued commercial catches such as prawns and fish are dependent on these systems. They provide protective shelter for many animals, including fish, and can also be a direct food source for manatees and dugongs, turtles, water fowl, some herbivorous fish and sea urchins. The roots and rhizomes of seagrasses also stabilise sediments and prevent erosion while the leaves filter suspended sediments and nutrients from the water column. Seagrass meadows are thus linked to other important marine habitats such as coral reefs, mangroves, salt marshes and oyster reefs (Björk M., Short F., Mcleod, E. and Beer, S. 2008). These plants sequester a considerable amount of carbon dioxide per year. They have higher carbon storage capacity than in terrestrial plants. Seagrasses are responsible for about 15% of the carbon storage in the ocean. Seagrass beds sequester between 0.012 to 1.33 metric tons of carbon per hectare per year (tC ha-1 yr-1). Management efforts are made so that the role of these plants in climate change abatement can reach its highest potential. This paper presents an overview of plants found in soft bottom communities, their biology, ecology, benefits, role in climate change abatement, threats, as well as the management efforts, tools and strategies to help support their resilience.

2.FRESHWATER PLANT LIFE
2.1CHARACTERISTICS OF A FRESHWATER ENVIRONMENT
Light penetration through the water column is very much reduced in freshwater environments. Carbon dioxide dissolved in water is in low concentration and is one of the limiting factors living submerged in water. Oxygen concentrations in the water and in thick tissues of the underwater plant are also low. Minerals and nutrients are scarce or dilute within the water medium since the water is constantly moving. Moving water (currents and waves) can be damaging to the organs of the plant.

2.2STRATEGY FOR LIVING UNDERWATER
Leaves are often so highly dissected to maximize surface-to-volume (S/V) ratio, for rapid diffusion of carbon dioxide into the chloroplasts of the cells by having proportionately greater surface area. Figure 1 shows an example of a dissected leaf.

Figure 1. Example of dissected leaf
Stomates are generally absent since it is useless for submerged plants, where water, not air, continually surrounds the photosynthetic organ. Xylem tissue (water transport) is very poorly developed, appropriate since much of the shoots are bathed in water. There are formations of aerenchyma (parenchyma tissue having large intercellular air spaces) which functions for storage of oxygen and to transport that gas to living tissues. It is also important in leaves for buoyancy so that the leaves are erect in the water having greater chance to be exposed in light used for photosynthesis.

2.3EXAMPLES OF FRESHWATER PLANTS IN SOFT BOTTOM COMMUNITIES Eurasian milfoil (Myriophyllum spicatum)
water-nymph (Najas gracillima)
hornwort (Ceratophyllum demersum)

pondweed (Potamogeton pectinatus)
elodea (Elodea canadensis)
mare's-tail (Hippuris vulgaris)

2.4ROLE OF FRESHWATER PLANTS
While most people are aware of the consequences of poor logging...
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