E179L Final

Orthophosphates and nitrates are nutrients that when present at high levels will lead to the growth of phytoplankton, algae, and vascular plants. Having an increase of growth of these organisms can lead to eutrophication of the aquatic environment. Having large amounts of algae present in an aquatic environment causes fluctuations in dissolved oxygen levels. During the day, algae and other plants will generate oxygen through photosynthesis. However, once it is night time, this oxygen will be consumed by the high levels of oxygen consuming bacteria that is feeding on the dead or decaying algae. This will decrease oxygen levels to a perilous low resulting in the death of other organisms living in these aquatic environments. An anoxic event, or complete lack of oxygen, is also possible with the presence of excessive nutrients such as orthophosphates and nitrates. This event would lead to the death of organisms.

Big Canyon is a tributary to the Newport Back Bay. There are non-native plants, specifically the Brazilian Pepper present at Big Canyon, which is known to kill mycorrhizal fungi. The killing of this fungi is very unideal and unwanted; there is a symbiotic relationship between mycorrhizal fungi and the roots of most native plants. What mycorrhizal fungi does, particularly, is facilitate the transfer of phosphorus from the soil to the plants. These non-native species will be removed, and this specific fungi will be introduced along with native plants, for their symbiotic relationship, to be sure that their establishment and survival in Big Canyon will be successful. Improving tidal flushing is another part of the restoration plan with the goal of keeping the movement of water.

Overall, it is known that the colder water is, the more dissolved oxygen it can hold. Conversely, warm water holds less oxygen than cold water. There is an inverse relationship between water temperature and levels of dissolved oxygen. During the winter and early spring, water temperature is low and dissolved oxygen is high. During the summer and fall, water temperature is high and dissolved oxygen is usually lower. Dissolved oxygen will be at 100% air saturation in a stable body of water without stratification. What 100% air saturation means is that there is an equilibrium within the water allowing it to hold as many oxygen molecules as it can. There are certain occurrences when dissolved oxygen actually exceeds 100% air saturation in water when there are also plants and phytoplankton that add more dissolved oxygen to the system.

Autotrophy is when organisms can make their own food through photosynthesis. In contrast, heterotrophy is when organisms cannot make their own food and rely on eating or absorbing it. Autotrophy is related to an autochthonous pond, and heterotrophy is related to an allochthonous pond. In autotrophic conditions, P/R ratios are greater than 1, which in heterotrophic conditions, P/R ratios are less than 1. In an unfortunate previous experiment, it was shown that the addition of orthophosphate can convert a heterotrophic, oligotrophic area into an autotrophic one that is essentially eutrophic. Other instances have shown that excess nitrates can also lead to eutrophication, resulting in a depletion of oxygen and the death of organisms.

Estuaries are the down spout, or the point at which large interior drainages enter, accumulate nutrients, and then leave to enter the ocean. Eutrophication is the result of having excess nutrients such as nitrate and phosphate because these nutrients lead to a significant growth of algae and vascular plants. When eutrophication occurs, organisms can die as a result of the depletion of oxygen. A way to decrease the risk for eutrophication is to reduce the amount of nitrate and orthophosphate present in estuaries. The establishment of natural treatment systems ,such as soil aquifer treatment and phytoremediation, would be a good way to reduce these excess nutrients. By preventing excess nutrients to promote the growth of phytoplankton, algae and vascular plants, eutrophication and depletion of dissolved oxygen can be prevented.

UCNRS San Joaquin Marsh Reserve is known as a “natural” habitat that has an extensive diversity of plants with varying depths and amount of open water. Within this extensive diversity of plants is an abundance of emergent vegetation, specifically California bulrush (Schoenoplectus californicus), Chairmaker’s bulrush (Schoenoplectus americanus), Alkali bulrush (Bolboschoenus maritimus), and cattails, such as broadleaf cattail (Typha latifolia). This along with a diversity of depths allows this habitat to be used by a large diversity of wildlife. In contrast, IRWD Natural Treatment System is known for having open, deep water with just a narrow ring of emergent vegetation located around the pond edges. This treatment system uses bacteria located on the bottom of the lake to remove nitrate and phosphate from the San Diego Creek water, improving the water quality upon return to the creek. The design of this treatment system makes it unusable for waterfowl such as ducks.

Reclaimed water promotes the growth of algae and vascular plants as these waters are high in nutrients such as nitrate and phosphate. Having a growth promotion of these certain organisms will lead to eutrophication. Mason Park Pond is completely artificial and man-made for humans. Mason Park Pond is eutrophic, and the cause of this is the use of reclaimed water, even though there is also stormwater. Mason Park actually has to pump air into the pond to make up for the low DO levels. The best way to solve the eutrophication of bodies of water is to refuse the use of reclaimed water. If reclaimed water is going to be used regardless, the next best option is setting up a natural treatment system. Non-reclaimed water such as rainwater and stormwater does not contain these nutrients and poses a much smaller threat.

Respiration in benthic water reduces its dissolved oxygen. Due to poor circulation, there is no replacement of the dissolved oxygen that was used in respiration resulting in lower DO than surface water, despite the colder temperatures. At the bottom, because of respiration occurring 24 hours of the day, these waters are often anoxic. In contrast, because of the input of oxygen from photosynthesis by plants and phytoplankton, dissolved oxygen levels at the surface are usually higher. Conversely, if there is a very shallow water column with very little phytoplankton present, the dissolved oxygen levels at the top will be almost identical to that of the bottom. In this case, if there is heat at the surface or more algae present at the bottom, there will be less dissolved oxygen present at the surface than the bottom.

By 2100, it is predicted that sea levels will rise 4 feet. This poses a threat to bay estuaries much like Back bay. One potential mitigation measure for climate change impacts would be preparing upstream sites, such as the San Joaquin Marsh, to eventually become a salt marsh as sea levels rise. Another option would be to allow sediments to continue their natural flow. Finally, restoring sediment flows to the coast is also a potential mitigation measure for climate change impacts. Because sea levels are rising, ironically it is an ideal time for the Big Canyon restoration.

For various reasons, such as the presence of phytoplankton and wind stirring, the top of the water column usually has more DO than the bottom, even when the top is warmer. The bottom would have a relatively steady state of low DO due to the fact that respiration constantly goes on for 24 hours. The surface will have variation with its DO levels as the day progresses. At dawn, DO is at the lowest level, and it will increase during the day. When photosynthetic output of DO commences, DO will begin to increase. DO levels will usually peak between noon and sunset. Finally, DO levels will decrease due to respiration and the 24-hour cycle will begin all over again.