St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants
St Helena is an isolated oceanic island located in the tropical South Atlantic, and knowledge of broadscale oceanography and productivity in its surrounding waters is limited. This study used model outputs (2007-2017), remote sensing data (1998-2017) and survey measurements (April 2018 and 2019) to...
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2021
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Online Access: | https://doi.org/10.3389/fmars.2021.655321 https://doaj.org/article/e74c7c82aff04a7196f8c871cc632c81 |
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ftdoajarticles:oai:doaj.org/article:e74c7c82aff04a7196f8c871cc632c81 2023-05-15T13:38:39+02:00 St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants Suzanne Jane Painting Eleanor K. Haigh Jennifer A. Graham Simon A. Morley Leeann Henry Elizabeth Clingham Rhys Hobbs Frances Mynott Philippe Bersuder David I. Walker Tammy Stamford 2021-06-01T00:00:00Z https://doi.org/10.3389/fmars.2021.655321 https://doaj.org/article/e74c7c82aff04a7196f8c871cc632c81 EN eng Frontiers Media S.A. https://www.frontiersin.org/articles/10.3389/fmars.2021.655321/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2021.655321 https://doaj.org/article/e74c7c82aff04a7196f8c871cc632c81 Frontiers in Marine Science, Vol 8 (2021) oceanography threshold indicator nutrient microbiology contaminant Science Q General. Including nature conservation geographical distribution QH1-199.5 article 2021 ftdoajarticles https://doi.org/10.3389/fmars.2021.655321 2022-12-31T16:25:01Z St Helena is an isolated oceanic island located in the tropical South Atlantic, and knowledge of broadscale oceanography and productivity in its surrounding waters is limited. This study used model outputs (2007-2017), remote sensing data (1998-2017) and survey measurements (April 2018 and 2019) to determine background conditions for nutrients, chlorophyll and suspended particulate matter (SPM) in offshore waters and propose standards (thresholds) for assessing inshore water quality based on 50% deviation from seasonal (usually June to November) or annual averages. Seasonal thresholds were proposed for surface nitrate (average 0.18 μM), phosphate (average 0.26 μM), silicate (average 2.60 μM), chlorophyll (average 0.45 μg chl l–1), and SPM (average 0.96 mg l–1). Associated background values for most surface parameters (phosphate 0.17 μM, silicate 1.57 μM, chlorophyll 0.30 μg chl l–1; from model outputs and remote sensing) were slightly higher than offshore observations (April 2019). For nitrate, the average background value (0.12 μM) was lower than the observed average (0.24 μM). At depth (150-500 m), annual background values from model outputs were high (nitrate 26.8 μM, phosphate 1.8 μM, silicate 17.3 μM). Observed water masses at depths >150 m, identified to be of Antarctic and Atlantic origin, were nutrient-rich (e.g., 16 μM for nitrate, April 2019) and oxygen deficient (<4-6 mg l–1). A thermocline layer (between ca. 10 and 230 m), characterized by a sub-surface chlorophyll maximum (average 0.3-0.5 μg chl l–1) near the bottom of the euphotic zone (ca. 100 m), is likely to sustain primary and secondary production at St Helena. For assessing inshore levels of chemical contaminants and fecal bacteria estimated from survey measurements, standards were derived from the literature. A preliminary assessment of inshore observations using proposed thresholds from surface offshore waters and relevant literature standards indicated concerns regarding levels of nutrients and fecal bacteria at some locations. More ... Article in Journal/Newspaper Antarc* Antarctic Directory of Open Access Journals: DOAJ Articles Antarctic St. Helena ENVELOPE(8.575,8.575,63.621,63.621) Frontiers in Marine Science 8 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
oceanography threshold indicator nutrient microbiology contaminant Science Q General. Including nature conservation geographical distribution QH1-199.5 |
spellingShingle |
oceanography threshold indicator nutrient microbiology contaminant Science Q General. Including nature conservation geographical distribution QH1-199.5 Suzanne Jane Painting Eleanor K. Haigh Jennifer A. Graham Simon A. Morley Leeann Henry Elizabeth Clingham Rhys Hobbs Frances Mynott Philippe Bersuder David I. Walker Tammy Stamford St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
topic_facet |
oceanography threshold indicator nutrient microbiology contaminant Science Q General. Including nature conservation geographical distribution QH1-199.5 |
description |
St Helena is an isolated oceanic island located in the tropical South Atlantic, and knowledge of broadscale oceanography and productivity in its surrounding waters is limited. This study used model outputs (2007-2017), remote sensing data (1998-2017) and survey measurements (April 2018 and 2019) to determine background conditions for nutrients, chlorophyll and suspended particulate matter (SPM) in offshore waters and propose standards (thresholds) for assessing inshore water quality based on 50% deviation from seasonal (usually June to November) or annual averages. Seasonal thresholds were proposed for surface nitrate (average 0.18 μM), phosphate (average 0.26 μM), silicate (average 2.60 μM), chlorophyll (average 0.45 μg chl l–1), and SPM (average 0.96 mg l–1). Associated background values for most surface parameters (phosphate 0.17 μM, silicate 1.57 μM, chlorophyll 0.30 μg chl l–1; from model outputs and remote sensing) were slightly higher than offshore observations (April 2019). For nitrate, the average background value (0.12 μM) was lower than the observed average (0.24 μM). At depth (150-500 m), annual background values from model outputs were high (nitrate 26.8 μM, phosphate 1.8 μM, silicate 17.3 μM). Observed water masses at depths >150 m, identified to be of Antarctic and Atlantic origin, were nutrient-rich (e.g., 16 μM for nitrate, April 2019) and oxygen deficient (<4-6 mg l–1). A thermocline layer (between ca. 10 and 230 m), characterized by a sub-surface chlorophyll maximum (average 0.3-0.5 μg chl l–1) near the bottom of the euphotic zone (ca. 100 m), is likely to sustain primary and secondary production at St Helena. For assessing inshore levels of chemical contaminants and fecal bacteria estimated from survey measurements, standards were derived from the literature. A preliminary assessment of inshore observations using proposed thresholds from surface offshore waters and relevant literature standards indicated concerns regarding levels of nutrients and fecal bacteria at some locations. More ... |
format |
Article in Journal/Newspaper |
author |
Suzanne Jane Painting Eleanor K. Haigh Jennifer A. Graham Simon A. Morley Leeann Henry Elizabeth Clingham Rhys Hobbs Frances Mynott Philippe Bersuder David I. Walker Tammy Stamford |
author_facet |
Suzanne Jane Painting Eleanor K. Haigh Jennifer A. Graham Simon A. Morley Leeann Henry Elizabeth Clingham Rhys Hobbs Frances Mynott Philippe Bersuder David I. Walker Tammy Stamford |
author_sort |
Suzanne Jane Painting |
title |
St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
title_short |
St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
title_full |
St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
title_fullStr |
St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
title_full_unstemmed |
St Helena Marine Water Quality: Background Conditions and Development of Assessment Levels for Coastal Pollutants |
title_sort |
st helena marine water quality: background conditions and development of assessment levels for coastal pollutants |
publisher |
Frontiers Media S.A. |
publishDate |
2021 |
url |
https://doi.org/10.3389/fmars.2021.655321 https://doaj.org/article/e74c7c82aff04a7196f8c871cc632c81 |
long_lat |
ENVELOPE(8.575,8.575,63.621,63.621) |
geographic |
Antarctic St. Helena |
geographic_facet |
Antarctic St. Helena |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
Frontiers in Marine Science, Vol 8 (2021) |
op_relation |
https://www.frontiersin.org/articles/10.3389/fmars.2021.655321/full https://doaj.org/toc/2296-7745 2296-7745 doi:10.3389/fmars.2021.655321 https://doaj.org/article/e74c7c82aff04a7196f8c871cc632c81 |
op_doi |
https://doi.org/10.3389/fmars.2021.655321 |
container_title |
Frontiers in Marine Science |
container_volume |
8 |
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1766109149411672064 |