Nutrients in sea water Introduction Distribution of Phosphorus and seasonal variation Distribution of nitrogen compounds Distribution of silicates and manganese

Introduction Nutrients are essential for plant growth Nutrients food Nitrogen (N) Phosphorus (P) Silicon(Si) The concentration in seawater varies from place to place In seawater nitrogen is the limiting nutrient Limiting nutrients are added for expensing algal population is fish culture ponds Photosynthesis

Distribution of phosphate and nitrate Distribution is characterized by four different layers. 1)A surface layer in which the concentration is low and relatively uniform with depth, 2)A layer in which the concentration increases rather rapidly with depth 3)A layer of maximum concentration that is usually located somewhere between 500 and 1500m, and 4)A thick bottom layer in which there is relatively little change with depth

Distribution of Phosphorus Marine organisms contain phosphorus in the form of orthophosphoric acid. The turnover rate of phosphorus in the surface layers is quite rapid. The phosphorus regeneration rate is thus a function of water temperature and the phytoplankton population. In the Atlantic ocean, water below about 1000m exhibits a decrease in phosphate as one move from south to north.

Maximum phosphate concentration (0.33ppm) are found north of the equator. The phosphate in the phototrophic regions of the oceans is normally depleted spring and summer. Phosphate is found in high values during winter and lowest during summer season About 50% of the total phosphorous in sea occurs in upper 60 m of sea.

Phosphorous is present in sea in sea as inorgonic form – phosphate 60% of phoshphorous in sea found in upper born of sea Phosphorous availability have impact on primary production rates River runoff and diffusion flux in ocean are source of phosphorous.

Distribution of Nitrogen compound Nitrate in the oceans is the end product of decomposition of organic nitrogen Decomposition-proceeds through organic nitrogen  ammonia  nitrite  nitrate in successive stages Plankton utilizes all the inorganic nitrogen forms for life process and in summer it deplets Nitrogen constitute 48% of dissolved gas in ocean water Nitrogen fixing bacteria - cyanobocteria convert nitrogen gas in to usable chemical form for marine life.

Ingeneration of nitrogen is accomplished mainly by bacterial action and chemical breakdown Nitrate is found in oceans in all depths in higher concentration than other forms of nitrogen The distribution of nitrate and phosphate are similar in oceans Nitrate concentration in Atlantic ocean is lower than in Indian or Pacific ocean. Surface waters of North and South Atlantic are richer in nitrate than deep waters of Atlantic ocean.

North Pacific ocean waters are higher in nitrates than south pacific waters. Deep waters of antartic ocean have concentrations up to 10-5ppm but surface waters are devoid of nitrate Nitrate along the 30⁰w longitude line are high compared to small nitrate concentration in tropical surface waters. Ammonium concentrations are found lower than the concentration of nitrates in surface water

Maximum concentration of Ammonium in surface water are found in fall and water and minimum concentration are found in spring season. In deep ocean layers ammonium content water are found at about 0.002ppm. Nitrite is found in very low concentrations at about few mg/cum and is found entirely in surface layers. Maximum nitrite concentration are found just below photic zone.

Distribution of silicate Silica is required as a nutrient by all organisms Necessary for the formation of skeletons for many diatoms Regeneration of silica appears to be due to chemical process rather than bacterial action Turnover time for silica is not known Silica concentrations vary widely in the oceans In upper layers where silica is used by biological organisms, concentrations of less than 0.014ppm are often found The concentration of silica increases with increasing depth.

Silicon cycle in sea Silicon Diatoms Death Deposited at sea bottom

Distribution of manganese Manganese occurs in sea water usually as a divalent ion. particulate manganese is not found in the sea except in surface waters. Found in low concentration range less than to about 0.01ppm.