User:Mbreuerco/Sacramento–San Joaquin River Delta

Peer Review

So far I have added several paragraphs of information detailing the presence of toxic cyanobacteria in the Sacramento-San Joaquin Delta. I provided multiple sources showing an increasing frequency of harmful algal blooms over the past several decades in the Delta. I also included information on the toxic effects of microcystins that are produced from the cyanobacteria. I need to work on condensing the information down as the pre-existing article is already not very large and the scale of the information should match the rest of the article. I also need to cut out parts that are not directly relevant to the Delta itself because there are other articles that already cover similar information where it would be better suited. I need feedback on how well my sentences flow and whether or not they would be readable to the general public. I would also like to know about the relevancy of my contributions to the article and whether or not information should be added or removed.

(Bottom of Ecology Section)

The Delta has seen numerous cyanobacteria blooms with increasing frequency over the past two decades. Cyanobacteria have the potential to produce cyanotoxins which can pose a risk to humans and animals upon contact. Because of this cyanobacteria blooms are seen as a threat that has the potential to impact human life. Several types of toxic cyanobacteria have appeared in the Delta, with Microcystis aeruginosa being one of the most common types. Microcystis aeruginosa produce microcystins which are hepatotoxins that can cause liver cancer. Frequent Microcystis blooms have impacted the food web of the Delta at multiple trophic levels. Microcystis spp. blooms in the Delta were found to decrease the diversity of the aquatic microbial community. Additionally, the cyanobacteria blooms in the Delta have led to decreased zooplankton mass and density. There is also concern for further spread throughout the food web via bioaccumulation. Microcystins were detected in the tissue of clams at levels much higher than the ambient water around them because of microcystin's ability to covalently bind to tissue.

The increased occurrences of cyanobacteria blooms in the Delta can be attributed to a variety of factors with the most important being lowered streamflow. From 2004 through 2008 researchers collected different water quality parameters during the cyanobacteria blooms and determined that the blooms appeared after reaching a threshold of 19°C (66°F) which was exacerbated by reduced precipitation, reduced streamflow, and increased nutrient concentrations. They also determined that the negative attributes associated with climate change like reduced precipitation and increased temperatures could further increase the possibility of cyanobacteria blooms in the Delta. The high prevalence of nutrient concentrations in the Delta also plays a significant part in the increased frequency of Microcystis aeruginosa blooms. Microcystis benefits greatly from anthropogenic inputs of nitrogen which allows it to out-compete other primary producers and dominate the lower trophic levels. There have also been large amounts of nutrients monitored in the Delta as a result of various human activities.

The increased presence of Microcystis aeruginosa blooms in the Delta represents a continual threat for species at multiple trophic levels. The lower trophic levels are affected from both reduced diversity as well as reduced numbers through competition. When the conditions are met Microcystis have the ability to dominate the lower trophic levels hence why they are able to bloom. Additionally, when microcystins are present in the system then the consumers in the food web are at risk due to the effects of bioaccumulation. Fish that are present and active during cyanobacteria blooms can often have microcystin levels high enough to produce sublethal effects. Because microcystins can concentrate inside fish at multiple trophic levels it also represents a risk for human consumption as well.

References