Historical records of coastal eutrophication-induced hypoxia

Gooday, Andrew J.; Jorissen, Frans; Levin, Lisa A.; Middelburg, Jack J.; Naqvi, S.W.A.; Rabalais, Nancy N.; Scranton, Mary I.; Zhang, J.

doi:10.5194/bg-6-1707-2009

Cited by 154 publications

(96 citation statements)

References 261 publications

(288 reference statements)

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“…They have also often been used as tracers of hypoxia (Osterman 2003;Tsujimoto et al 2006;Gooday et al 2009). Important changes in the foraminifer assemblage are recorded in the upper 8 cm of core COR05-37.…”

Section: Discussionmentioning

confidence: 99%

“…The relative abundance of certain species, such as Bulimina marginata, Elphidium excavatum, Nonionellina labradorica, Lagena sp., and Glandulina sp., decreases sharply and some of the taxa disappear towards the sediment-water interface. The reason for changes in foraminifer abundances cannot be assessed unequivocally since the tolerance limits of these species to the physical and chemical properties of water masses are poorly known (Sen Gupta and Machain-Castillo 1993;Gooday et al 2009). Nevertheless, the general decrease in species diversity probably reflects an additional stress, which could have been caused by the lowering of DO concentrations.…”

Section: Discussionmentioning

confidence: 99%

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Recent changes in bottom water oxygenation and temperature in the Gulf of St. Lawrence: Micropaleontological and geochemical evidence

Genovesi

Vernal

Thibodeau

et al. 2011

Limnology & Oceanography

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Micropaleontological and geochemical analyses of a sediment core collected in the Laurentian Trough of the Gulf of St. Lawrence were carried out to reconstruct temporal variations in pelagic productivity and benthic environmental conditions. Dinoflagellate cyst assemblages reveal relatively stable pelagic productivity over the last two centuries. Similarly, geochemical (organic C, C org : N) and isotopic (d 13 C org , d 15 N) data reveal that organic matter fluxes to the seafloor have been relatively constant over the same period. In contrast, significant changes are recorded in the benthic foraminifer assemblages. A sediment surface peak in the abundance of Cassidulina laevigata and Brizalina subaenariensis is consistent with the recent record of oxygen depletion in the bottom water. A decrease in the relative abundance of Nonionellina labradorica, concomitant with a relatively higher occurrence of Oridorsalis umbonatus in the upper part of the core, reflects a significant warming of the bottom water. Changes in bottom-water properties are further constrained by a negative trend of the d 18 O in Bulimina exilis carbonate shells over the last century, corresponding to a warming of about 2uC. These results strongly suggest that the recent oxygen depletion in the bottom waters of the Gulf of St. Lawrence is due to changes in water masses that have led to increased bottom-water temperatures and, to some extent, a resultant increase in organic matter respiration rates.Eutrophication is often identified as the main cause of bottom-water hypoxia (, 2 mg L 21 or 62.5 mmol L 21 ) in coastal environments (Cloern 2001). In the Lower St. Lawrence Estuary (LSLE), direct measurements have documented a progressive depletion of dissolved oxygen (DO) in bottom waters (. 250 m), from , 125 to 60 mmol L 21 over the last 80 yr (Gilbert et al. 2005). These observations are consistent with results of micropaleontological and geochemical analyses of sediment cores that show clear evidence of bottom-water oxygen depletion since the 1960s (Thibodeau et al. 2006). Whereas one half to two thirds of the oxygen depletion has been ascribed to a change in ocean circulation in the northwest Atlantic and, thus, variations in the water properties (DO, temperature, salinity) of the bottom waters that enter the Gulf and St. Lawrence through Cabot Strait (Gilbert et al. 2005), the remainder has been speculatively associated with increased organic carbon (C org ) fluxes to the seafloor, possibly due to anthropogenic eutrophication (Thibodeau et al. 2006). Thibodeau et al. (2006) and Gilbert et al. (2007) have shown that increases in sales of agricultural fertilizers, especially nitrogen fertilizers, in the St. Lawrence River drainage basin are concurrent with the depletion of bottom-water oxygen concentrations in the LSLE. Finally, an increase in bottom-water temperatures (Gilbert et al. 2005), leading to increased respiration rates, could also explain the recent decrease of DO concentrations.To determine if eutrophication and the trend ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Recent changes in bottom water oxygenation and temperature in the Gulf of St. Lawrence: Micropaleontological and geochemical evidence

Genovesi

Vernal

Thibodeau

et al. 2011

Limnology & Oceanography

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“…This is especially true in examining stress-sensitive species and community threshold dynamics/responses. Coastal hypoxia (low dissolved oxygen DO < 2 mL L −1 ; Diaz and Rosenberg, 2008) and anoxia have become recognized as a key emerging problem in the last decades, with an increasing number of affected sites coupled with increasing intensity, frequency and duration of events (Gooday et al, 2009;Rabalais et al, 2010;Zhang et al, 2010, see;also this issue and references therein). Adequate measurements to monitor the impacted fauna and identify sensitive and more tolerant species is therefore pivotal, especially when the course of oxygen decline is rapid, e.g.…”

Section: Introductionmentioning

confidence: 99%

CellTracker Green labelling vs. rose bengal staining: CTG wins by points in distinguishing living from dead anoxia-impacted copepods and nematodes

et al. 2013

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Abstract. Hypoxia and anoxia have become a key threat to shallow coastal seas. Much is known about their impact on macrofauna, less on meiofauna. In an attempt to shed more light on the latter group, in particular from a process-oriented view, we experimentally induced short-term anoxia (1 week) in the northern Adriatic Sea (Mediterranean) and examined the two most abundant meiofauna taxa – harpacticoid copepods and nematodes. Both taxa also represent different ends of the tolerance spectrum, with copepods being the most sensitive and nematodes among the most tolerant. We compared two methods: CellTracker Green (CTG) – new labelling approach for meiofauna – with the traditional rose bengal (RB) staining method. CTG binds to active enzymes and therefore colours live organisms only. The two methods show considerable differences in the number of living and dead individuals of both meiofauna taxa. Generally, RB will stain dead but not yet decomposed copepods and nematodes equally as it does live ones. Specifically, RB significantly overestimated the number of living copepods in all sediment layers in anoxic samples, but not in any normoxic samples. In contrast, for nematodes, the methods did not show such a clear difference between anoxia and normoxia. RB overestimated the number of living nematodes in the top sediment layer of normoxic samples, which implies an overestimation of the overall live nematofauna. For monitoring and biodiversity studies, the RB method might be sufficient, but for more precise quantification of community degradation, especially after an oxygen depletion event, CTG labelling is a better tool. Moreover, it clearly highlights the surviving species within the copepod or nematode community. As already accepted for foraminiferal research, we demonstrate that the CTG labelling is also valid for other meiofauna groups.

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“…Evidence from biological paleoindicators (reviewed by Gooday et al, 2009) illustrates how communities of indicator The increased preservation of organic matter under anoxic conditions typically leads to elevated organic carbon content (Hartnett et al, 1998), and sediments overlain by anoxic waters are often also enriched in trace metals (Tribovillard et al, 2006). Sediment Chesapeake Bay (Adelson et al, 2001) and the Baltic Sea (Jilbert and Slomp, 2013).…”

Section: Chemical Clues To Historic Changementioning

confidence: 99%