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Early Eocene deep-sea benthic foraminiferal faunas: recovery from the Paleocene Eocene Thermal Maximum extinction in a greenhouse world
Get PDFThe early Eocene greenhouse world was marked by multiple transient hyperthermal events. The most extreme was the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), linked to the extinction of the globally recognised deep-sea benthic foraminiferal Velasco fauna, which led to the development of early Eocene assemblages. This turnover has been studied at high resolution, but faunal development into the later early Eocene is poorly documented. There is no widely accepted early Eocene equivalent of the Late Cretaceous-Paleocene Velasco fauna, mainly due to the use of different taxonomic concepts. We compiled Ypresian benthic foraminiferal data from 17 middle bathyal-lower abyssal ocean drilling sites in the Pacific, Atlantic and Indian Oceans, in order to characterise early Eocene deep-sea faunas by comparing assemblages across space, paleodepth and time. Nuttallides truempyi, Oridorsalis umbonatus, Bulimina trinitatensis, the Bulimina simplex group, the Anomalinoides spissiformis group, pleurostomellids, uniserial lagenids, stilostomellids and lenticulinids were ubiquitous during the early Eocene (lower-middle Ypresian). Aragonia aragonensis, the Globocassidulina subglobosa group, the Cibicidoides eocaenus group and polymorphinids became ubiquitous during the middle Ypresian. The most abundant early Ypresian taxa were tolerant to stressed or disturbed environments, either by opportunistic behavior (Quadrimorphina profunda, Tappanina selmensis, Siphogenerinoides brevispinosa) and/or the ability to calcify in carbonate-corrosive waters (N. truempyi). Nuttallides truempyi, T. selmensis and other buliminids (Bolivinoides cf. decoratus group, Bulimina virginiana) were markedly abundant during the middle Ypresian. Contrary to the long-lived, highly diverse and equitable Velasco fauna, common and abundant taxa reflect highly perturbed assemblages through the earliest Ypresian, with lower diversity and equitability following the PETM extinction. In contrast, the middle Ypresian assemblages may indicate a recovering fauna, though to some extent persistently disturbed by the lower-amplitude Eocene hyperthermals (e.g., Eocene Thermal Maximum 2 and 3). We propose the name ‘Walvis Ridge fauna’ for future reference to these Ypresian deep-sea benthic foraminiferal assemblages
Convolutional Neural Networks for Phytoplankton identification and classification
Get PDFPhytoplankton form the basis of the marine food web and are an indicator for the overall status of the marine ecosystem. Changes in this community may impact a wide range of species (Capuzzo et al. 2018) ranging from zooplankton and fish to seabirds and marine mammals. Efficient monitoring of the phytoplankton community is therefore essential (Edwards et al. 2002). Traditional monitoring techniques are highly time intensive and involve taxonomists identifying and counting numerous specimens under the light microscope. With the recent development of automated sampling devices, image analysis technologies and learning algorithms, the rate of counting and identification of phytoplankton can be increased significantly (Thyssen et al. 2015). The FlowCAM (Álvarez et al. 2013) is an imaging particle analysis system for the identification and classification of phytoplankton. Within the Belgian Lifewatch observatory, monthly phytoplankton samples are taken at nine stations in the Belgian part of the North Sea. These samples are run through the FlowCAM and each particle is photographed. Next, the particles are identified based on their morphology (and fluorescence) using state-of-the-art Convolutional Neural Networks (CNNs) for computer vision. This procedure requires learning sets of expert validated images. The CNNs are specifically designed to take advantage of the two dimensional structure of these images by finding local patterns, being easier to train and having many fewer parameters than a fully connected network with the same number of hidden units.In this work we present our approach to the use of CNNs for the identification and classification of phytoplankton, testing it on several benchmarks and comparing with previous classification techniques. The network architecture used is ResNet50 (He et al. 2016). The framework is fully written in Python using the TensorFlow (Abadi, M. et al. 2016) module for Deep Learning.Deployment and exploitation of the current framework is supported by the recently started European Union Horizon 2020 programme funded project DEEP-Hybrid-Datacloud (Grant Agreement number 777435), which supports the expensive training of the system needed to develop the application and provides the necessary computational resources to the users
Marine biological value along the Portuguese continental shelf; insights into current conservation and management tools
Get PDFThe valuation of nature is an inbuilt component of validating environmental management decisions and an important research field for different disciplines related to conservation, economy and ethics. Here, biodiversity was valued using an ecological approach based on the intrinsic value incorporated in biodiversity per se, regardless of any human association. The Marine Biological Valuation protocol was drawn upon the methodology of terrestrial valuation maps, to support the European MSFD environmental status assessment (descriptor 1 – biodiversity) and national marine spatial planning approaches. To apply the protocol on the Portuguese continental shelf we compiled and analyzed national biological databases for a wide taxonomic range of ecosystem components (seabirds, demersal fish, macrobenthos, marine mammals and sea turtles) and assessed the spatial overlap with existing and proposed conservation areas (Natura 2000 network). The resultant maps described patterns of biological value consistent with the physical and biological oceanographic conditions as well as local hydrodynamics of the Portuguese continental shelf. The results of our approach confirm previously identified valuable areas for protection (particularly in the northern and central regions), but also highlights the value of currently unprotected sites, mainly in the southern region. Biological valuation maps showed to be comprehensive tool to compile and spatially analyze biological datasets. By drawing attention to subzones of biological importance, it constitutes a valuable instrument in making appropriate-scale decisions on the spatial allocation of human activities in the context of the Portuguese marine spatial planning, currently facing the pressure and impacts of increased maritime exploitation
Quantification of chemical and mechanical bioerosion rates of six Caribbean excavating sponge species found on the coral reefs of Curaçao
Get PDFExcavating sponges are among the most important macro-eroders of carbonate substrates in marine systems. Their capacity to remove substantial amounts of limestone makes these animals significant players that can unbalance the reef carbonate budget of tropical coral reefs. Nevertheless, excavating sponges are currently rarely incorporated in standardized surveys and experimental work is often restricted to a few species. Here were provide chemical and mechanical bioerosion rates for the six excavating sponge species most commonly found on the shallow reef of Curaçao (southern Caribbean): Cliona caribbaea, C. aprica, C. delitrix, C. amplicavata, Siphonodictyon brevitubulatum and Suberea flavolivescens. Chemical, mechanical and total bioerosion rates were estimated based on various experimental approaches applied to sponge infested limestone cores. Conventional standing incubation techniques were shown to strongly influence the chemical dissolution signal. Final rates, based on the change in alkalinity of the incubation water, declined significantly as a function of incubation time. This effect was mitigated by the use of a flow-through incubation system. Additionally, we found that mechanically removed carbonate fragments collected in the flow-through chamber (1 h) as well as a long-term collection method (1 wk) generally yielded comparable estimates for the capacity of these sponges to mechanically remove substratum. Observed interspecific variation could evidently be linked to the adopted boring strategy (i.e. gallery-forming, cavity-forming or network-working) and presence or absence of symbiotic zooxanthellae. Notably, a clear diurnal pattern was found only in species that harbour a dense photosymbiotic community. In these species chemical erosion was substantially higher during the day. Overall, the sum of individually acquired chemical and mechanical erosion using flow-through incubations was comparable to rates obtained gravimetrically. Such consistency is a first in this field of research. These findings support the much needed confirmation that, depending on the scientific demand, the different approaches presented here can be implemented concurrently as standardized methods
A transcriptomic approach to unravel fatty acid pathways of harpacticoid copepods in a changing environment
Get PDFOn the relationships between macrobenthos activities and sediment oxygen dynamics - A case study in the Schelde estuary
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Marine phytoplankton community composition data from the Belgian part of the North Sea, 1968-2010
Get PDFThe Belgian Phytoplankton Database (BPD) is a comprehensive data collection comprising quantitative phytoplankton cell counts from multiple research projects conducted since 1968. The collection is focused on the Belgian part of the North Sea, but also includes data from the French and the Dutch part of the North Sea. The database includes almost 300 unique sampling locations and more than 3,000 sampling events resulting in more than 86,000 phytoplankton cell count records. The dataset covers two periods: 1968 to 1978 and 1994 to 2010. The BPD can be accessed online and provides high quality phytoplankton count data. The species taxonomy is updated, and the count values are quality checked and standardized. Important metadata like sampling date, sampling location, sampling depth and methodology is provided and standardized. Additionally, associated abiotic data and biovolume values are available. The dataset allows to conduct analyses of long-term temporal and spatial trends in phytoplankton community structure in the southern part of the North Sea, including changes in phytoplankton phenology and seasonality
