Phytoplankton and nutrients in the Helgoland region

摘要: During recent decades, phytoplankton stock on the one hand and inorganic nutrients (P bound N) other have increased considerably in southern North Sea, as demonstrated at a permanent station (since 1962) near island Helgoland. This correlation between P N need not anything to do with causality; exceptional algal blooms been observed reported literature since 19th century. Furthermore, these increases (four-fold for two-fold nutrients) are same range fluctuations from year under different hydrographical conditions. A detailed investigation carried out 1981 presence of slowly growing population. Starting considerable flagellates spring, it reached peak cell numbers over long reproduction period which contrasted normal duration spring bloom diatoms. These processes were related limited production by or N. concentration was permanently available form compounds. The total amount surpassed far portion incorporated phytoplankton. is consequence fact that small organisms high metabolic rate. Therefore, relation (daily ≈stock) completely known e.g. agriculture. exist during vegetation mainly dissolved organic matter accessible plankton. great dynamics this system, including phase shifting P, N, Si, production, indicates significance fast remineralization. Calculations demonstrate natural nutrient content seawater normally satisfies demands present Sea area study. Only more productive coastal region (salinity<30 associated fresh water run-offs low — an unrealistic assumption German Bight) might some limitation be observed. For diatoms, silicate may represent critical component, but dynamic force exists Si concentrations. lack silicon must any limitation; however, knowledge system insufficient up now.