Ecosystem, euphotic zone

Fasham, M.3.R., 1985. A flow analysis of materials in the marine euphotic zone. In R.E. Ulanowicz and T. Platt (eds), Ecosystem Theory for Biological Oceanography. Can. Bull. Fish. Aquat. Sci., 213 139-162. 

Most modem N-cycle models simulate N export using one or the other of these approaches, but details vary and some models combine aspects of expHcit sinking and reminerahzation with Martin curve parameterizations. For example, Chai et al (1996) modeled a 5-component N-based ecosystem including a detrital N compartment with explicit sinking, but did not permit detrital remineralization within the euphotic zone. In contrast, Christian et al (2002a) used a Martin curve to redistribute detrital N vertically, but rather than remineralizing at the specified depth, it is returned to the... 

In contrast to terrestrial ecosystems, the fundamental limitation of primary production in the ocean is not irradiance per se, but temperature and the concentration of chlorophyll in the upper ocean. The latter is a negative feedback i.e., the more the chlorophyll in the water column, the shallower is the euphotic zone. Hence, to double NPP requires nearly a fivefold increase in chlorophyll concentration. 

With these conditions and c [uestions in mind, why is P more often limiting in lakes than on land, at least in the temperate zone P limits lake productivity because (a) unlike C and N, there are no mechanisms that can increase inputs of P when it is in short supply, as discussed above (b) P is relatively immobile within and through terrestrial ecosystems, so inputs of P to lakes are small and (c) lakes have an uncontrollable loss of P, in the sinking of particulate organic matter out of the euphotic zone. 

In the Nanshan Island coral reef ecosystems, the deficiencies of Th with respect to 238 j observed within the euphotic zone and the nitracline zone, which responded to two maximums of photosynthetic pigments. All of these reflected the differential zones where two vertically distinct phytoplankton assemblages lived. Excessive total Th over found at depth... 

These nutrients that are supplied from the seabed during summer are transported to the head of the bay by the estuarine circulation. Furthermore, they are again uptaken into the upper water, and are used for the increase in the phytoplanktons in the euphotic zone. Estuarine circulation plays a key role in the nutrient cycles of stratified estuaries by increasing the retention, recycling the nutrients, and stabilizing the ecosystem. ... 

---