User:Mbreuerco/sandbox/sacramento-san-joaquin-delta

(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. 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.

References


 * 1) ^ Jump up to:a b c d Lehman, P.W., Marr, K., Boyer, G.L., Acuna, S., and Teh, S.J. (2013) Long-term trends and causal factors associated with Microcystis abundance and toxicity in San Francisco Estuary and implications for climate change impacts. Hydrobiologia 718: 141-158.
 * 2) ^ Mankiewicz-Boczek, Joanna & WALTER, ZOFIA & Zalewski, Maciej & Konopnickiej, M.. (2002). Natural toxins from cyanobacteria. Acta Biol. Cracov Bot. 45.
 * 3) ^ Zegura, Bojana & Sedmak, Bojan & Filipic, Metka. (2003). Microcystin-LR induces oxidative DNA damage in human hepatoma cell line HepG2. Toxicon : official journal of the International Society on Toxinology. 41. 41-8. 10.1016/S0041-0101(02)00207-6.
 * 4) ^ Jump up to:a b Otten, T.G., Paerl, H.W., Dreher, T.W., Kimmerer, W.J. and Parker, A.E. (2017), The molecular ecology of Microcystis sp. blooms in the San Francisco Estuary. Environ Microbiol, 19: 3619-3637. doi:10.1111/1462-2920.13860
 * 5) ^ Stringfellow, William. (2013). Unprecedented Bloom of Toxin-Producing Cyanobacteria in the Southern Bay-Delta Estuary and its Potential Negative Impact on the Aquatic Food-Web (Report 4.5.1). 10.13140/RG.2.1.3730.3768.
 * 6) ^ Jump up to:a b Bolotaolo M, Kurobe T, Puschner B, et al. Analysis of Covalently Bound Microcystins in Sediments and Clam Tissue in the Sacramento-San Joaquin River Delta, California, USA. Toxins (Basel). 2020;12(3):178. Published 2020 Mar 13. doi:10.3390/toxins12030178
 * 7) ^ Mioni, Cecile & Kudela, Raphael & Baxa, Dolores. (2011). Harmful cyanobacteria blooms and their toxins in Clear Lake and the Sacramento-San Joaquin Delta (California). Report Prepared for Central Valley Regional Water Quality Control Board.
 * 8) ^ Jump up to:a b Noriko Takamura, Toshio Iwakuma, Masayuki Yasuno, Uptake of 13 C and 15 N (ammonium, nitrate and urea) by Microcystis in Lake Kasumigaura, Journal of Plankton Research, Volume 9, Issue 1, 1987, Pages 151–165, https://doi.org/10.1093/plankt/9.1.151
 * 9) ^ Kraus, T.E.C., Bergamaschi, B.A., and Downing, B.D., 2017, An introduction to high-frequency nutrient and biogeochemical monitoring for the Sacramento–San Joaquin Delta, northern California: U.S. Geological Survey Scientific Investigations Report 2017–5071, 41 p., https://doi.org/10.3133/sir20175071.
 * 10) ^ Berg M and Sutula M. 2015. Factors affecting the growth of cyanobacteria with special emphasis on the Sacramento-San Joaquin Delta. Southern California Coastal Water Research Project, Technical Report 869 August 2015.