An official website of the United States government
Abstract We investigated the biogeography of benthic foraminifera in a highly urbanized tropical seascape, i.e. Hong Kong, in order to assess their utility as bioindicators relative to other marine fauna. Hong Kong is one of the largest coastal cities on the planet and studies of other benthic fauna in the region are available for comparison. We found that: (1) turbid, muddy habitats host a unique foraminiferal fauna; (2) areas with intermediate levels of eutrophication have the highest foraminiferal species diversity; (3) semi-enclosed and heavily polluted environments host a distinct foraminiferal fauna, characterized by low taxonomic diversity and/or high dominance, and that is acclimated to stressful marine conditions. Biodiversity patterns of foraminifera in Hong Kong are generally consistent with those of other soft-sediment macro- and meio-fauna (e.g. polychaetes, molluscs and ostracods); however, foraminifera may be more sensitive than these other groups to eutrophication and associated changes in coastal food webs. The tolerance of some, but not other, species to eutrophic and hypoxic conditions means that foraminiferal faunas can serve as bioindicators across a wide array of environmental conditions, in contrast with corals whose sensitivity to eutrophication results in their absence from eutrophied settings. The well-known autoecology of foraminifera taxa can help to characterize environmental conditions of different habitats and regional environmental gradients. Although the use of fauna as bioindicators may be most robust when data are compared for multiple taxonomic groups, when such broad sampling is not available, benthic foraminifera are particularly well suited for environmental assessments due to their ubiquity, interspecific environmental breadth, and the well-understood environmental preference of individual taxa.
more »
« less
EARLY JURASSIC BENTHIC FORAMINIFERAL ECOLOGY FROM THE CENTRAL HIGH ATLAS MOUNTAINS, MOROCCO
Abstract The Central High Atlas Mountains of Morocco have an extensive record of Lower Jurassic deposits from the Tethyan Ocean. In the Amellago region, Ziz Valley, and Dadès Valley several fossilized reef outcrops preserve benthic foraminifera spanning the Pliensbachian and Toarcian stages. This study analyzes benthic foraminiferal assemblage changes across the bi-phased extinctions at the Pliensbachian/Toarcian boundary and the Jenkyns Event (also referred to as the Toarcian Oceanic Anoxic Event). In Pliensbachian samples, assemblages with abundant Glomospira sp., Glomospirella sp., Siphovalvulina sp., Haurania deserta, Placopsilina sp., Mesoendothyra sp., and Everticyclammina praevirguliana are observed. Following both the Pliensbachian/Toarcian boundary event and the Jenkyns Event, benthic foraminiferal density, evenness, and species richness decreased, indicating these communities underwent ecologic stress; however, loss of diversity was most substantial between samples that pre-date and post-date the Jenkyns Event. Whereas the Pliensbachian/Toarcian boundary event coincides with the demise of the large benthic foraminifera Mesoendothyra sp. and Everticyclammina praevirguliana, the Jenkyns Event was detrimental for most clades of benthic foraminifera, including many small, resilient taxa. Based on the evidence provided, we suggest that the Pliensbachian/Toarcian boundary and the Jenkyns Event were distinct events, potentially caused by distinct environmental perturbations.
more »
« less
- Award ID(s):
- 1848393
- PAR ID:
- 10585068
- Publisher / Repository:
- SEPM
- Date Published:
- Journal Name:
- Palaios
- Volume:
- 39
- Issue:
- 8
- ISSN:
- 0883-1351
- Page Range / eLocation ID:
- 277 to 299
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Dissolution of carbonate platforms, like The Bahamas, throughout Quaternary sea-level oscillations have created mature karst landscapes that can include sinkholes and off-shore blue holes. These karst features are flooded by saline oceanic waters and meteoric-influenced groundwaters, which creates unique groundwater environments and ecosystems. Little is known about the modern benthic meiofauna, like foraminifera, in these environments or how internal hydrographic characteristics of salinity, dissolved oxygen, or pH may influence benthic habitat viability. Here we compare the total benthic foraminiferal distributions in sediment-water interface samples collected from <2 m water depth on the carbonate tidal flats, and the two subtidal blue holes Freshwater River Blue Hole and Meredith’s Blue Hole, on the leeward margin of Great Abaco Island, The Bahamas. All samples are dominated by miliolid foraminifera (i.e.,QuinqueloculinaandTriloculina), yet notable differences emerge in the secondary taxa between these two environments that allows identification of two assemblages: a Carbonate Tidal Flats Assemblage (CTFA) vs. a Blue Hole Assemblage (BHA). The CTFA includes abundant common shallow-water lagoon foraminifera (e.g.,Peneroplis,Rosalina,Rotorbis), while the BHA has higher proportions of foraminifera that are known to tolerate stressful environmental conditions of brackish and dysoxic waters elsewhere (e.g.,Pseudoeponides,Cribroelphidium,Ammonia). We also observe how the hydrographic differences between subtidal blue holes can promote different benthic habitats for foraminifera, and this is observed through differences in both agglutinated and hyaline fauna. The unique hydrographic conditions in subtidal blue holes make them great laboratories for assessing the response of benthic foraminiferal communities to extreme environmental conditions (e.g., low pH, dysoxia).more » « less
-
Assessing potential for diagenetic overprinting of climatic signals in benthic foraminifera: Preliminary results. Robert K. Poirier, Reinhard Kozdon, Maureen Raymo, Morgan Schaller Benthic foraminiferal stable isotope records (δ18O, δ13C) are the most common paleoclimate records produced to date, which capture changes in temperature, ice volume, and the global carbon system on orbital to sub-millennial timescales. General relationships between deep sea δ18O and sea level have long been established, and more recent paired δ18O and Mg/Ca records seek to disentangle the temperature and ice volume components of corresponding sea level records. However, the extent to which diagenesis may potentially alter the original isotopic signature recorded in tests of benthic foraminifera remains relatively undefined. We present preliminary results of a project focused on constraining the extent to which such diagenetic overprinting might alter sea level estimates based on records produced from modern to mid-Pliocene Cibicidoides and Uvigerina specimens. These include advanced imaging techniques (SEM, CL-spectroscopy), single shell stable isotope analyses (δ18O, δ13C), and chamber wall trace metal profiles (LA-ICPMS) paired with in situ δ18O analyses (SIMS). In addition, we present strict specimen screening criteria developed based on a new quantitative assessment of visual preservation in both individual foraminiferal tests and whole assemblages. http://forams2018.wp.st-andrews.ac.uk Session II: Advances in Foraminiferal Geochemistry Conveners: Jelle Bijma, Howard Spero Session Overview: http://forams2018.wp.st-andrews.ac.uk/program/more » « less
-
Abstract Foraminifera are unicellular organisms that inhabit the oceans. They play an important role in the global carbon cycle and record valuable paleoclimate information through the uptake of trace elements such as strontium into their calcitic shells. Understanding how foraminifera control their internal fluid composition to make calcite is important for predicting their response to ocean acidification and for reliably interpreting the chemical and isotopic compositions of their shells. Here, we model foraminiferal calcification and strontium partitioning in the benthic foraminiferaCibicides wuellerstorfiandCibicidoides mundulusbased on insights from inorganic calcite experiments. The numerical model reconciles inter-ocean and taxonomic differences in benthic foraminifer strontium partitioning relationships and enables us to reconstruct the composition of the calcifying fluid. We find that strontium partitioning and mineral growth rates of foraminiferal calcite are not strongly affected by changes in external seawater pH (within 7.8–8.1) and dissolved inorganic carbon (DIC, within 2100–2300 μmol/kg) due to a regulated calcite saturation state at the site of shell formation.more » « less
-
Abstract Geochemical records generated from the calcite tests of benthic foraminifera, especially those of the generaCibicidoidesandUvigerina, provide the basis for proxy reconstructions of past climate. However, the extent to which benthic foraminifera are affected by postdepositional alteration is poorly constrained. Furthermore, how diagenesis may alter the geochemical composition of benthic foraminiferal tests, and thereby biasing a variety of proxy‐based climate records, is also poorly constrained. We present the Foraminiferal Preservation Index (FPI) as a new metric to quantify preservation quality based on objective, well‐defined criteria. The FPI is used to identify and quantify trends in diagenesis temporally, from late Pliocene to modern coretop samples (3.3–0 Ma), as well as spatially in the deep ocean. The FPI identifies the chemical composition of deep‐ocean water masses to be the primary driver of diagenesis through time, while also serving as a supplementary method of identifying periods of changing water mass influence at a given site. Additionally, we present stable isotope data (δ18O, δ13C) generated from individualCibicidoidesspecimens of various preservation quality that demonstrate the likelihood of significant biasing in a variety of geochemical proxy records, especially those used to reconstruct past changes in ice volume and sea level. These single‐test data further demonstrate that when incorporating carefully selected tests of only the highest preservation quality, robust paleorecords can be generated.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2110/palo.2023.026
