Benthic foraminifera and their response to hydrography, periodic hypoxic conditions and primary production in the Koljö fjord on the Swedish west coast

Gustafsson, Mikael; Nordberg, Kjell

doi:10.1016/s1385-1101(99)00002-7

Cited by 70 publications

(59 citation statements)

References 23 publications

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“…Commonly used methods such as maintaining the sediment cores under anoxic conditions for some time would kill only a fraction of the animal community. For example, nematodes, which were abundant in the sediment, and other groups of meiofauna are tolerant of anoxic conditions (e.g., Fenchel & Riedl 1970, Bernard & Fenchel 1996, Moodley et al 1997, Vopel et al 1998, Gustafsson & Nordberg 1999. Also, moderate heating of the sediment would unlikely kill all animals.…”

Section: Discussionmentioning

confidence: 99%

Effects of bioturbation on solutes and solids in marine sediments

Berg¹,

Rysgaard²,

Funch³

et al. 2001

Aquat. Microb. Ecol.

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Bioturbation, the mixing of solutes and solids in sediments caused by movements of fauna, was studied through tracer experiments and numerical modeling. The generally accepted mathematical formulation of transport by bioturbation as a diffusive process was applied and values of the biodiffusivity (D B ) were estimated for both dissolved and solid constituencies in the same sediment. Two independent estimates were found for each constituency. For solutes, D B was determined from incubated sediment cores after addition of bromide to the overlying water and subsequent modeling of the bromide depth-distributions in the sediment. D B for solutes was also estimated by comparing interpretations of measured concentration-depth profiles and fluxes of O 2 . For solids, D B was estimated from modeling the depth-distributions of glass beads, which were added to the sediment surface in the same cores as used for the bromide tracer experiments. In addition, D B , also for solids, was determined by interpretations of 2 measured 210 Pb depth profiles. We validated our findings through sensitivity analyses and comparisons to other studies. As part of this process we tested if irrigation, the pumping activity of tube-dwelling animals, could influence our results. It is commonly assumed that the same D B value applies to both the bioturbation of solutes and solids. Our analyses, however, show clearly that the effects of bioturbation on solutes are many fold stronger than on solids, as reflected in the estimated D B value of 4.6 ± 1.0 × 10 -6 (1 SE) cm 2 s -1 for solutes and a value that is 15 to 20 times smaller for solids. The results also show that the transport of solutes by bioturbation is equally as important as molecular diffusion in the upper sediment layers (few cm). Since the density and species composition of fauna in the studied sediment were comparable to those at many other near-shore marine sites, we believe that our results are general for many sediments. We suggest that the recognized mathematical formulation of bioturbation as a diffusive process be extended to include 2 different biodiffusivities, one for solutes and one for solids.KEY WORDS: Bioturbation · Biodiffusivity · Pore water · Sediments · Meio-and macrofauna Resale or republication not permitted without written consent of the publisher

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Section: Discussionmentioning

confidence: 99%

Effects of bioturbation on solutes and solids in marine sediments

Berg¹,

Rysgaard²,

Funch³

et al. 2001

Aquat. Microb. Ecol.

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“…Culturing experiments also demonstrated that under suboptimal environmental conditions (e.g., 10 • C, Bradshaw, 1957), this species can remain alive for long periods without growing or reproducing. In nature, dormancy has been suggested as survival strategy under adverse conditions such as anoxia (Bernhard and SenGupta, 1999;Gustafsson and Nordberg, 1999;Polovodova et al, 2009). It is not impossible for episodic hypoxia events to occur in the muddy organic-rich environments of the upper and middle areas of the Auray estuary.…”

Section: Benthic Foraminiferal Stable Isotopes (δ 18 O and δ 13 C) Inmentioning

confidence: 99%

Interpretation of benthic foraminiferal stable isotopes in subtidal estuarine environments

et al. 2009

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Abstract.Here we present a novel approach for the interpretation of stable isotope signatures recorded in benthic foraminifera from subtidal estuarine environments. The stable isotopic composition (δ 18 O and δ 13 C) of living Ammonia tepida and Haynesina germanica is examined at four stations in the Auray River estuary (Gulf of Morbihan, France) sampled in two contrasting seasons, spring 2006 and winter 2007. Comparing benthic foraminiferal δ 18 O measurements with theoretical oxygen isotopic equilibrium values, calculated on the basis of water temperature and salinity measurements in the upper and lower estuary, i.e., T-S-δ 18 O eq. diagrams, strongly suggests that foraminiferal faunas sampled at the four stations calcified during different periods of the year. This interpretation can be refined by using the benthic foraminiferal δ 13 C, which is mainly determined by the mixing of sea and river water. In the upper estuary foraminifera mainly calcified in early spring and winter, whereas in the lower estuary calcification mainly took place in spring, summer and autumn. This new method provides insight into the complexity of estuarine benthic foraminiferal stable isotope records. In addition, it can also be used to obtain new information on preferred calcification periods of benthic foraminiferal taxa in different parts of the estuary.

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“…Zillén and Conley (2010) show that, especially during the last two millennia, phases of hypoxia such as during the early medieval expansion (700-1300 AD) seem to correlate with major changes in population and land use in Scandinavia instead of correlating with natural climate variations. Some of the fjords of southwest Sweden, e.g., the Gullmar Fjord off the Skagerrak, have been studied extensively, especially with respect to changes in hydrography, eutrophication, and oxygen status (Gustafsson and Nordberg, 1999, 2000Eriksson et al, 2002;Nordberg, 2004a, b, 2010;Filipsson et al, 2004;Erlandsson et al, 2006;Polovodova et al, 2011;Polovodova Asteman et al, 2013). Due to their relatively small area, fjords provide ideal settings for monitoring changes in water mass conditions.…”

Section: Introductionmentioning

confidence: 99%

Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

Groeneveld

Filipsson

2013

Biogeosciences

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Abstract. Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing climate change and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future, it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g., stable isotopes and trace metal/Ca ratios, that are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are significantly different or as conditions can change much faster compared to the open ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions in bottom water on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected, we assume it unlikely that any diagenetic coatings have already significantly affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the calcite saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios from G. turgida can potentially be related to variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens that lived deeper in the sediment than those that lived near the surface. G. turgida samples from the low-oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when bottom water dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations, but an additional impact of the inorganic carbonate chemistry cannot be excluded.

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Benthic foraminifera and their response to hydrography, periodic hypoxic conditions and primary production in the Koljö fjord on the Swedish west coast

Cited by 70 publications

References 23 publications

Effects of bioturbation on solutes and solids in marine sediments

Effects of bioturbation on solutes and solids in marine sediments

Interpretation of benthic foraminiferal stable isotopes in subtidal estuarine environments

Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

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