Dataset Information

Bryozoan zooid size variation across a bathymetric gradient: a case study from the Icelandic shelf and continental slope.

ABSTRACT: Body size is one of the most important biological characters, as it defines many aspects of organismal functioning at the individual and community level. As body size controls many ecological aspects of species, it is often used as a proxy for the status of the ecosystem. So far no consistent mechanism driving size shift has been proposed. In this study, we investigated bathymetric variability in zooid's size and shape in aquatic colonial animals, Bryozoa. Although the response of bryozoan zooid size to temperature or food concentration has been experimentally proven, the effects of natural environmental variability on marine bryozoan populations has been much less explored. The presented investigation is aimed to assess the bathymetric patterns and environmental drivers of bryozoan zooid size on continental shelf and slope of southern Iceland. 196 colonies of 11 species representing different colonial forms and taxonomic groups were selected for zooid characteristics measurements. A pattern of depth-related increase in zooid size was documented for Bicellarina alderi, Chartella barleei and Sarsiflustra abyssicola, no statistically significant effects were detected for the other eight species. Two species Bicellarina alderi and Caberea ellisii had significantly longer zooids in deeper water, shape of the remaining species did not change along the bathymetric gradient. Intercolonial coefficient of variation in zooid size did not change across the depth gradient. Temperature differences along studied depth could be responsible for the observed pattern.

SUBMITTER: Stepien A

PROVIDER: S-EPMC5589789 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Bryozoan zooid size variation across a bathymetric gradient: a case study from the Icelandic shelf and continental slope.

Stępień Anna A Kukliński Piotr P Włodarska-Kowalczuk Maria M Krzemińska Małgorzata M Gudmundsson Gudmundur G

Marine biology 20170907 10

Body size is one of the most important biological characters, as it defines many aspects of organismal functioning at the individual and community level. As body size controls many ecological aspects of species, it is often used as a proxy for the status of the ecosystem. So far no consistent mechanism driving size shift has been proposed. In this study, we investigated bathymetric variability in zooid's size and shape in aquatic colonial animals, Bryozoa. Although the response of bryozoan zooid ...[more]

PMID: 28943656

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Project description:Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.

Project description:Recent expeditions have revealed high levels of biodiversity in the tropical deep-sea, yet little is known about the age or origin of this biodiversity, and large-scale molecular studies are still few in number. In this study, we had access to the largest number of solariellid gastropods ever collected for molecular studies, including many rare and unusual taxa. We used a Bayesian chronogram of these deep-sea gastropods (1) to test the hypothesis that deep-water communities arose onshore, (2) to determine whether Antarctica acted as a source of diversity for deep-water communities elsewhere and (3) to determine how factors like global climate change have affected evolution on the continental slope. We show that although fossil data suggest that solariellid gastropods likely arose in a shallow, tropical environment, interpretation of the molecular data is equivocal with respect to the origin of the group. On the other hand, the molecular data clearly show that Antarctic species sampled represent a recent invasion, rather than a relictual ancestral lineage. We also show that an abrupt period of global warming during the Palaeocene Eocene Thermal Maximum (PETM) leaves no molecular record of change in diversification rate in solariellids and that the group radiated before the PETM. Conversely, there is a substantial, although not significant increase in the rate of diversification of a major clade approximately 33.7 Mya, coinciding with a period of global cooling at the Eocene-Oligocene transition. Increased nutrients made available by contemporaneous changes to erosion, ocean circulation, tectonic events and upwelling may explain increased diversification, suggesting that food availability may have been a factor limiting exploitation of deep-sea habitats. Tectonic events that shaped diversification in reef-associated taxa and deep-water squat lobsters in central Indo-West Pacific were also probably important in the evolution of solariellids during the Oligo-Miocene.

Dataset Information

Bryozoan zooid size variation across a bathymetric gradient: a case study from the Icelandic shelf and continental slope.

Publications

Bryozoan zooid size variation across a bathymetric gradient: a case study from the Icelandic shelf and continental slope.

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