Description of time series:
Between 2013 and 2017 the average concentration levels of chlorophyll a levels showed no significant trend but are above the 90th percentile.
Description of gauge:
The gauge value of 90 indicates that between 2013 and 2017 the average concentration levels of chlorophyll ɑ in the Gulf of Alaska were considerably above the median of all chlorophyll ɑ concentration levels between 1998 and 2017
Description of Chlorophyll a:
At the base of most marine food webs are microscopic plants, called phytoplankton - which also produce nearly half of the Earth’s oxygen. One way we measure the amount of phytoplankton in the ocean is via a pigment that phytoplankton produce - chlorophyll a. Using ocean color sensors on satellites, we can measure the amount of chlorophyll a in surface waters. Environmental and oceanographic factors continuously influence the abundance, composition, spatial distribution, and productivity of phytoplankton. Tracking the amount of phytoplankton in the ocean gives us the status of the base of the food web, and how much food is available for other animals to grow. Changes in the amount of phytoplankton in the ocean are part of the natural seasonal cycle, but can also indicate an ecosystem’s response to a major external disturbance.
Overall Scores mean the following:
- 0 - 10: “significantly lower” the long term median state
- 10 - 25: “considerably lower” the long term median state
- 25 - 50: “slightly lower” the long term median state
- 50: the long term median state
- 50 - 75: “slightly above” the long term median state
- 75 - 90 “considerably above” the long term median state
- 90 - 100: “significantly higher” the long term median state
High values of Chlorophyll a can be good (lots of big nutrious diatoms) or bad (Harmful Algal Blooms), depending on the species present.
Chlorophyll a data were obtained from the NOAA Fisheries Coastal & Oceanic Plankton Ecology, Production, & Observations Database. Measurements of ocean chlorophyll concentration were combined from both the SeaWiFS and MODIS-Aqua "ocean color" datasets and binned at 0.5 x 0.5 degree latitude-longitude boxes, annual averages for each year calculated from the average of all monthly means in that year, and the annual mean was calculated as the average of all annual means. Source: https://www.st.nmfs.noaa.gov/copepod/about/about-copepod.html.