Variable coastal hypoxia exposure and drivers across the southern California Current

Low, Natalie H. N.; Micheli, Fiorenza; Aguilar, J.D.; Arce, Daniel Romero; Boch, Charles A.; Bonilla, Juan Carlos; Bracamontes, Miguel Ángel; Leo, Giulio De; Díaz, Eduardo López; Enríquez, Eduardo; Hernández, Arturo; Martínez, Ramón; Mendoza, Ramón; Miranda, Claudia; Monismith, Stephen G.; Ramade, Mario; Rogers‐Bennett, Laura; Romero, Alfonso; Salinas, Carmina; Smith, Alexandra; Torre, Jorge; Villavicencio, Gustavo; Woodson, C. Brock

doi:10.1038/s41598-021-89928-4

Cited by 26 publications

(14 citation statements)

References 58 publications

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“…Other parameters influencing DO level in water are temperature and salinity (Song et al 2019 ). The optimal range of DO is 4–9 mg/L, which largely supports the diverse fish population and it is known that DO values receding below 2 mg/L would result in hampering the sustainment of juvenile fishes and crustaceans (Low et al 2021 ). DO level of Ghoghla beach water at all transects had an average of 5.61±0.28, 4.76±0.18 and 4.40±0.11 mg/L during pre-lockdown, lockdown and post-lockdown phases, whereas the trend observed in Somnath beach water was different (3.56±0.77, 4.55±0.19 and 2.97±0.72 mg/L).…”

Section: Resultsmentioning

confidence: 93%

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

Sahoo

Sonpal

Chanchpara

et al. 2022

Environ Sci Pollut Res

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Environmental impact of COVID-19 imposed lockdown (2020) and the new normal condition (2021) on two different beaches of India (Ghoghla beach, Diu and Somnath beach, Veraval) were compared with the pre-lockdown era, 2013. The lockdown phase favored the natural restoration of the beaches and showed infinitesimal values of the parameters tested when compared with the pre-lockdown regime. However, the new normal situation in 2021 opened up the accessibility of these beaches to the tourists and pilgrims resulting in significant changes of water quality. The release of diluted sewage mixed with freshwater from the Somnath town to the sea has led to the drastic change in beach water quality. The mean cadmium concentration increased drastically in beach waters (Ghoghla: 1.35, 0.28 and 7.09 μg/L; Somnath: 0.45, 0.28 and 0.58 μg/L) during pre-to-post lockdown, respectively. However, post-lockdown resulted in the rise of toxic heavy metals in the sediments of Somnath beach but Ghoghla beach remained to be pristine which may be due to the Blue Flagship status. The total number of marine bacteria was higher during 2013 and 2021 when compared during lockdown describing greater human interventions. For instance, Vibrio spp. count in Ghoghla beach water during pre-lockdown phase was 7733 CFU/mL and this value reduced to 70 and 5 CFU/mL in the lockdown and post-lockdown phases. Interestingly, the diversity of planktonic and benthic components showed a different trend from pre-to-post lockdown due to significant change in the inorganic nutrients and metal bioaccumulation. To our knowledge, this will be the first comprehensive assessment to report the environmental and ecological health of Ghoghla beach and Somnath beach during the pre-to-post lockdown. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-022-21586-z.

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Section: Resultsmentioning

confidence: 93%

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

Sahoo

Sonpal

Chanchpara

et al. 2022

Environ Sci Pollut Res

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“…In turn, these impacts scale up to population level, species composition, biodiversity, and commercial fisheries (e.g., Grantham et al, 2004;Vaquer-Sunyer and Duarte, 2008;Ekau et al, 2010;Low and Micheli, 2018;Thomas and Rahman, 2012). Moreover, severe impacts on marine organisms or even mas mortality events of fish and invertebrates are commonly associated with EBUS, where hypoxia frequently occurs (Grantham et al, 2004;Low et al, 2021). Thus, alterations in upwelling regimes as a consequence of climate change are likely to further increase the frequency and magnitude of upwelling-driven hypoxia and, in consequence, mass mortality events (Stauffer et al, 2012).…”

Section: Impact and Risks Of Hypoxiamentioning

confidence: 99%

“…Vulnerability to hypoxia is variable across temporal and spatial scales (Low et al, 2021) and this is the case in central Chile. Since vulnerability is dependent on economic, sociocultural, geographic, demographic, and governance factors (Kelman, et al, 2016;Low et al, 2021), the Chilean coast could be considered as highly vulnerable to hypoxia. In Chile there are 100 coastal municipalities with around 4.5 million inhabitants.…”

Section: Impact and Risks Of Hypoxiamentioning

confidence: 99%

“…Thus, a monitoring network of academic, government, fishing cooperatives and social stakeholders could provide a valuable opportunity for local adaptation in the face of escalating exposure to environmental stressors (Low et al, 2021). Capacity building, community participation and adequate governance in coastal communities regions will help to reduce socio-economic impacts associated with these events.…”

Section: Impact and Risks Of Hypoxiamentioning

confidence: 99%

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The intensification of coastal hypoxia off central Chile: Long term and high frequency variability

Maza

2023

Front. Earth Sci.

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Hypoxia is a phenomenon where dissolved oxygen (DO) is reduced to levels that are low enough to strongly affect ecological and biogeochemical processes. This occurs within the continental shelf off central Chile (36°S), influenced by seasonal coastal upwelling (Spring-Summer). Monthly measurements of DO and other oceanographic variables in the water column (1997−2021) over the 92 m isobath along with high-resolution and near-surface observations (POSAR buoy), are analyzed to examine incidences of hypoxia and understand the physical and biogeochemical processes modulating DO vertical distribution and its temporal variability. On average, the percentage of the water column with DO levels below 89 (hypoxia) and 22 (severe hypoxia) μmol L−1 reaches 68% (i.e., hypoxic waters are found below 30 m) and 44% (below 50 m depth), respectively, but during the upwelling season, as much as 87% (below 12 m depth) and 81% (below 17 m depth) of the water column exhibits these levels. On the sub-seasonal scale during upwelling season six hypoxic events lasting at least 2 days occur at 10 m depth. There is a strong seasonal correlation between the volume of the seawater presenting hypoxia and upwelling favorable winds. Furthermore, there is a high DO interannual variability partially related to the El Niño Southern Oscillation (ENSO). Over 2 decades, it is estimated that DO concentration in surface and subsurface layers decreases (up to 21 μmol L−1 decade−1) as waters get colder (up to 0.29°C decade−1). Remarkably, the volume of hypoxic and severe hypoxic waters over the shelf has increased more than 2 times since 1997 and shows a significant positive correlation with the upwelling index. These preliminary findings indicate that the increase in local DO consumption is partially associated with upwelling intensification. Given the clear evidence of wind intensification in coastal upwelling ecosystems and thus the increase in hypoxic events, the coastal zone may be highly vulnerable to hypoxia, impacting biological resources and biogeochemical cycles.

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“…Most work on the underlying causes of coastal hypoxia have focused on nutrient loading and increasing temperatures associated with climate change (e.g., Meire et al, 2013;Low et al, 2021). For example, increasing water temperatures result in a decrease in DO solubility (Keeling et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Temperature sensitivity of oxygen demand varies as a function of organic matter source

Szewczyk

Smith²,

Benítez-Nelson³

2023

Front. Mar. Sci.

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Dissolved oxygen (DO) impairment within coastal waters is widespread and rising temperatures may exacerbate low DO levels by enhancing organic matter (OM) degradation. Here, the temperature sensitivity of OM degradation was investigated as DO decay rates determined during standard five-day biochemical oxygen demand (BOD) measurements conducted under different incubation temperatures. Sampling was conducted in the Waccamaw River watershed, South Carolina, a blackwater river with extensive forested wetland that also receives drainage from stormwater detention ponds associated with coastal development, thus providing different sources of contrasting OM composition. Temperature sensitivities were measured as Q10 temperature coefficients, which define how DO decay rates change with 10 degrees of warming. The average Q10 value for the wetland sites (2.14 ± 0.41) was significantly greater (p < 0.05) than those measured in either the River (1.49 ± 0.36) or stormwater ponds (1.41 ± 0.21). Furthermore, using Intergovernmental Panel on Climate Change intermediate-to-very high temperature estimates for 2100 of +2.7 – 4.4°C, average predicted increases in DO decay rates for wetlands (~22-39%) are more than double the River (~11-18%) and stormwater pond rates (~9-16%). Our findings for inland, coastal waters agree with previous results for soils, suggesting that temperature sensitivities are variable across sites and increase with more complex, lower quality OM. Future modeling scenarios of DO utilization must therefore consider the influence of OM heterogeneity and the temperature sensitivity response of OM degradation across sources and region to better predict how climate change may impact oxygen impairment in aquatic ecosystems.

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Variable coastal hypoxia exposure and drivers across the southern California Current

Cited by 26 publications

References 58 publications

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

Pre-to-post COVID-19 lockdown and their environmental impacts on Ghoghla beach and Somnath beach, India

The intensification of coastal hypoxia off central Chile: Long term and high frequency variability

Temperature sensitivity of oxygen demand varies as a function of organic matter source

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