A response by benthic Foraminifera to the deposition of phytodetritus in the deep sea
TL;DR: Evidence is presented that certain small benthic Foraminifera (within the meiofaunal size-range) react dramatically to the presence of phytodetritus, suggesting that some deep-sea bentho-foramina are specialist feeders that bloom opportunistically when the appropriate food becomes available, while others remain unaffected by the organic influx.
Abstract: A recent major discovery has been the rapid sedimentation of phytodetritus to the deep-sea floor1–3 Although benthic mega-faunal invertebrates appear to seek out this relatively fresh food source1,4, and its seasonal arrival on the sea floor may synchronize reproduction in some echinoderms5, a convincing response by ben-thic organisms to phytodetritus has not been demonstrated3. Here I present evidence that certain small benthic Foraminifera (within the meiofaunal size-range) react dramatically to the presence of phytodetritus. Fresh aggregates of this material harbour abundant, low-diversity populations of these protists. The three commonest species are usually poorly represented in the more diverse assemblages inhabiting the underlying sediment. These findings suggest that some deep-sea benthic Foraminifera, like their shallow-water relatives6–8, are specialist feeders that bloom opportunistically when the appropriate food (phytodetritus and associated micro-organisms) becomes available, while others remain unaffected by the organic influx.
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01 Jan 2006TL;DR: This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level and demonstrates how living foraminifera can be used to monitor modern-day environmental change.
Abstract: In this volume John Murray investigates the ecological processes that control the distribution, abundance, and species diversity of benthic foraminifera in environments ranging from marsh to the deepest ocean. To interpret the fossil record it is necessary to have an understanding of the ecology of modern foraminifera and the processes operating after death leading to burial and fossilisation. This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level. It demonstrates how living foraminifera can be used to monitor modern-day environmental change. Ecology and Applications of Benthic Foraminifera presents a comprehensive and global coverage of the subject using all the available literature. It is supported by a website hosting a large database of additional ecological information (www.cambridge.org/0521828392) and will form an important reference for academic researchers and graduate students in Earth and Environmental Sciences.
1,479 citations
TL;DR: In this paper, the authors review benthic foraminiferal distribution patterns in the context of their use as proxy to reconstruct paleoenvironments, in particular against the background of relevant biological data, and conclude that species distribution with depth is mainly a function of organic flux and oxygenation.
566 citations
TL;DR: New records from the South Atlantic are presented that show rapid changes during the last deglaciation that were instantaneous (within dating uncertainty) and of opposite sign to those observed in the North Atlantic.
Abstract: The asynchronous relationship between millennial-scale temperature changes over Greenland and Antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the Atlantic Ocean. Here we present new records from the South Atlantic that show rapid changes during the last deglaciation that were instantaneous (within dating uncertainty) and of opposite sign to those observed in the North Atlantic. Our results demonstrate a direct link between the abrupt changes associated with variations in the Atlantic meridional overturning circulation and the more gradual adjustments characteristic of the Southern Ocean. These results emphasize the importance of the Southern Ocean for the development and transmission of millennial-scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide.
498 citations
19 Jun 1990-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this article, it has been shown that macroaggregates originating from the euphotic zone settle at a rate of approximately 100-150 m d -1 to form a deposit (phytodetritus) on the sediment surface.
Abstract: Most of the photosynthetically produced organic material reaching the ocean-floor is transported as settling particles, among which larger particles such as faecal pellets and macroaggregates (marine snow) are particularly important. Recent studies in the northeastern Atlantic have demonstrated that macroaggregates originating from the euphotic zone settle at a rate of approximately 100-150 m d -1 to form a deposit (phytodetritus) on the sediment surface. Bacteria and protozoa (flagellates and foraminifers) rapidly colonize and multiply on phytodetritus, while large deposit feeding animals ingest it. Other inputs, for example Sargassum , wood and vertebrate carcasses, also evoke a rapid response by benthic organisms. However, the taxa that respond depend on the form of the organic material. The intermittent or seasonally pulsed nature of phytodetritus and many other inputs regulate the population dynamics and reproductive cycles of some responding species. These are often opportunists that are able to utilize ephemeral food resources and, therefore, undergo rapid fluctuations in population density. In addition, the patchy distribution of much of the organic material deposited on the ocean-floor probably plays a major role in structuring deep-sea benthic ecosystems.
489 citations
TL;DR: In this article, the response by a deep-sea benthic community to a pulse of natural organic matter occurs within days, and in terms of activity and biomass, this rapid response was evident to a sediment depth of 9 cm.
Abstract: SEASONAL productivity in shallow waters elicits a seasonal pat-tern of activity in the benthic community1. This implies a very rapid response to fluctuations in the food supply to the benthos. Although there is a seasonal component to oxygen consumption on the deep-sea floor2 and a rapid response of epibenthic foraminifera3 and other microorganisms to influx of phytodetritus4, the timescale of the response of organisms that inhabit the sediment itself has not been established. Here I present evidence that the response by a deep-sea benthic community to a pulse of natural organic matter occurs within days. In terms of activity and biomass, this rapid response was evident to a sediment depth of 9 cm.
463 citations
References
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TL;DR: In this article, a similar seasonal pulse of detrital material to bathyal and abyssal depths in temperate latitudes is presented, this material seems to be derived directly from the surface primary production and to sink rapidly to the deep-sea benthos.
Abstract: Until recently the deep sea was considered to be a particularly stable environment1, free from seasonal variations. However, atmospheric storms may cause periodicity in deep-ocean currents2 and nepheloid layers3 while seasonality in the particulate flux to the deep sea is known to occur in the Sargasso Sea4,5 and Panama Basin6. Evidence is presented here of a similar seasonal pulse of detrital material to bathyal and abyssal depths in temperate latitudes; this material seems to be derived directly from the surface primary production and to sink rapidly to the deep-sea benthos. Considerable sedimentation occurs soon after the spring bloom and continues throughout the early summer. This process acts as a pathway for the descent of carbon from the euphotic zone, providing a periodic food source for the deep pelagic and benthic communities.
922 citations
TL;DR: In this article, an analysis of living (stained) benthic foraminifera within the upper 15 cm of deep-sea sediments, which reveals species-specific microhabitat preferences, with distinct morphological features found with epifaunal and infaunal species.
Abstract: Benthic foraminifera are protozoans found throughout the deep-sea environment, secreting a test of calcium carbonate or constructing a test of cemented sediment particles (agglutinated or arenaceous foraminifera). In typical deep-sea sediments, the organic cement of agglutinated taxa degrades upon burial in the sediment and, consequently, few specimens survive in the fossil record. In contrast, calcareous species are well preserved in most oceanic sediments, except at abyssal depths where most carbonate sediment is dissolved because of high levels of carbonate under-saturation of the bottom waters. Although benthic foraminifera have been widely used in studies of Cenozoic palaeoceanography, little is known about the ecology of deep-sea species. I present here an analysis of living (stained) benthic foraminifera within the upper 15 cm of deep-sea sediments, which reveals species-specific microhabitat preferences, with distinct morphological features found with epifaunal and infaunal species. The existence of infaunal habitats suggests that the distribution of certain foraminifera is not directly controlled by overlying bottom-water conditions, but by physicochemical conditions within the sediments. The microhabitat preferences may also explain interspecific carbon isotope differences, as existing data show that infaunal foraminifera generally have lower δ13C isotope values than epifaunal species.
792 citations
01 Aug 1985
TL;DR: A free-fall benthic time-lapse camera and current meter system has been used to examine changes in the appearance of the sea bed in the Porcupine Seabight 50°N, 13°W in the northeast Atlantic.
Abstract: A free-fall benthic time-lapse camera and current meter system has been used to examine changes in the appearance of the sea bed in the Porcupine Seabight 50°N, 13°W — northeast Atlantic). Changes in the benthic environment due to rapid deposition of phytodetritus occur down to 4000 m. Photograhs taken every 8 h from 1 May to mid-August showed dramatic changes in the appearance of the sea bed between mid-June and mid-July. The sinking rate of the detritus was calculated from the time of the spring bloom until its arrival on the sea bed. In both 1982 and 1983, year which differed greatly in the timing of the spring bloom, the sinking rates were probably between 100 and 150 m d−1. Individual aggregates up to 12 mm diameter arrived between frames at all depths and up to 50 mm at 4000 m. Their subsequent disintegration was monitored over the few days following arrival on the sea bed. Some such aggregates were collected from the sea bed and a sinking rate experiment was carried out on them.
Once on the sea bed, the detrital carpet moves over the sediment surface due to bottom currents; when currents exceed about 7 cm s−1 (at 1 m altitude), the material is resuspended. Increases in the quantity in suspension occur at the same time as decreases in the quantity visible on the sea bed. The tidal nature of the current gives a strong tidal component to the variation in suspended particles near the sea bed.
The significance of a detrital critical erosion threshold to the structure of benthic and benthopelagic communities is discussed.
606 citations
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