1. What are mean flows? How are these flows controlled in tropical vs. temperate systems? Explain critical abiotic and biotic factors in tropical systems using energy circuit language.
Mean flows can be described as the net energy, carbon, nitrogen, and phosphorus that move through an ecosystem. This incorporates many biotic and abiotic factors, which affect the speed and amount of energy or nutrients through the ecosystem. Looking at the Odum model of energy circuit (Mann 11) clearly shows the transition from source to another. Starting with primary producers initially increasing biomass by photosynthesis or providing a food source for heterotrophs, then loss of biomass via respiration and finally showing the net production. This then moves…show more content… Prior to human interaction, the Bay was a highly productive ecosystem and high in nutrients. However, with now 14 million people living on the watershed, the bay has become so polluted that some places have gone hypoxic (Mann 153). With The Bay being very large and relatively shallow, surface mixing of nutrients yields high amounts of phytoplankton. Furthermore, with loss of large marine plants and increased toxic algal blooms, most of the Bay has become hypoxic. Figure 1 shows what a normal estuary should look like compared to that of the Chesapeake Bay. Studies conducted in the 1970’s show that with increasing population growth a direct correlation could be made showing increase of nitrogen and phosphorous in the water of the Bay. Normally, nitrogen would be a limiting factor however, with an increase of nitrogen and phosphorous input, there was an increase in phytoplankton. Moreover, with air pollution being at a high, acid rain adds more nutrients to the waters. With increase of phytoplankton, sunlight is blocked and macrophytes are not able to photosynthesize and thus die. Furthermore, as seen in figure 1, with the death of phytoplankton, oxygen levels decrease especially when temperature increases. The epifauna are not able to survive this hypoxic environment and in turn die. However, with this increase of populations, unregulated fishing occurs and thus results in lowered species diversity and loss of commercial epifauna. Water quality has also decreased further from addition of suspended solids due erosion of the shoreline. With the addition of homes and destruction of natural forests, the shoreline continues to erode and increase the suspended solids in the waters. (Phillips, USGS: Scientific Solutions for a Healthy Bay and