| Title | Surface Chlorophyll a concentration and Secchi depth data from the SEAHAB project, March 2023 |
|---|---|
| Authors |
Smith, Marie |
| Publisher | Department of Forestry, Fisheries and the Environment (2025) |
| Contributors |
Project Member: Hughes, Lloyd Contact Person: Smith, Marie Rights Holder: Swiss Tropical and Public Health Institute |
| Abstract | This was the in situ data collection for the Sensor-agnostic Estimation of Harmful Algal Blooms (SEAHAB) project, March 2023. The data represents two days of surface water sampling between Table Bay and Kommetjie for the purpose of satellite chlorophyll a concentration and water clarity validation. |
| Methods | Secchi depth was measured using a weighted 30cm diameter white disk, which was lowered into the water until it can no longer be seen by the observer; the Secchi depth is the depth of the water at the point when the Secchi disk disappears/reappears. Surface seawater samples were collected in 2L plastic bottles, sealed and kept cool and in the dark until filtration on the same day. Filtration volumes ranged between 100 and 200 ml per sample. Samples were filtered onto GF/F filters (Whatman, diameter 25 mm, nominal pore size 0.7 um) and extracted in 90% acetone for 24h in the dark at -20 degrees Celcius, then measured with a Trilogy Laboratory Fluorometer following Welschmeyer (1994): Welschmeyer, N.A. Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnol. Oceanog. 1994, 39, 1985–1992. |
| Data | |
| Temporal extent | 27 Mar 2023 – 31 Mar 2023 |
| Geographic extent |
Table Bay; South African West Coast; Benguela Upwelling
North: -33.82369 |
| Vertical extent |
Max: -0.5 m Min: 0 m |
| Keywords | Algal Blooms , Chlorophyll a , EBV: Ecosystem Function > Primary productivity , EOV: Biochemistry > Particulate matter , EOV: Biology and Ecosystems > Phytoplankton biomass and diversity , SDG 14 Life Below Water , SDG 14.1.1 (a) , SEAHAB , Secchi depth , Sensor-agnostic Estimation of Harmful Algal Blooms (SEAHAB) project , SOUTH ATLANTIC OCEAN |