Indicator Of Oceanographic Conditions Research Articles

Calcareous microorganisms as indicators of oceanographic conditions in South West Atlantic Ocean

Abstract The results of multivariate analysis applied to the associations of benthic foraminifers and ostracods from surface sediments of the north Argentine continental shelf are presented in this study. We evaluated the distribution patterns and ecological preferences of species found in modern sediments from the north Argentine continental shelf, at depths between 15 and 130 m. We identified 61 species of foraminifers corresponding to the orders Rotaliida, Miliolida, Lagenida, Buliminida, Lituolida and Trochamminida, in addition to 18 species of ostracods that belong to the suborder Podocopina. The distribution of the ostracods Bradleya kaeslery Ramos, Coimbra and Whatley was extended to higher latitudes. It was determined that water depth and temperature were the factors that most affected the distribution of both types of microorganisms. Based on these data, we established three physiographical zones, which could be linked to the different water masses. In addition, the western limit of the Malvinas current at 80 m of water depth was corroborated. Our study highlights the potential use of benthic foraminifers and ostracods individuals as bioindicators for identifying oceanographic conditions in the Argentine continental shelf.

Position-dependent radiocarbon content of the macroalgae Undaria pinnatifida as an indicator of oceanographic conditions during algal growth

The radiocarbon content (∆14C) of the large brown macroalga Undaria pinnatifida was investigated as an indicator of oceanographic conditions during algal growth in Otsuchi Bay on the Pacific coast of northeastern Japan. In this region, warm boundary currents characterized by high dissolved inorganic carbon (DIC) ∆14C and cold subarctic Oyashio Current (low ∆14C-DIC) flow into the bay seasonally. We hypothesized that ∆14C values in U. pinnatifida pinnae (leaflet-like structures arising sequentially along the vertical axis of the blade) reflect ∆14C-DIC values in bay water during photosynthetic production. During the U. pinnatifida cultivation period (November 2013–April 2014), the Oyashio intrusion occurred from early March to early April, accompanied by a decrease in bay water ∆14C-DIC, from 15.7 ± 8.6‰ to − 57.1 ± 20.7‰. The ∆14C of the pinnae reflected ∆14C-DIC, as pinnae that formed in early March had significantly higher ∆14C (3.0 ± 5.4‰) than those that formed in early April (− 23.6 ± 7.5‰). These results indicate that the ∆14C of U. pinnatifida pinnae can serve as a record of Oyashio intrusion into the bay during algal growth.

The giant squid Architeuthis: An emblematic invertebrate that can represent concern for the conservation of marine biodiversity

The current public perception is that there is little reason for concern for the conservation of marine invertebrates, in part due to the scarcity of emblematic species to represent that diverse group. This paper shows that giant squid can be considered an emblematic species to represent concern for the conservation of marine invertebrate biodiversity because it satisfies all the requirements of an emblematic species. It shows that Architeuthis attracts public interest and attention and can serve as an indicator of oceanographic conditions and ocean climate change. It asserts that Architeuthis can represent concerns for vulnerable marine ecosystems associated with submarine canyons and that it belongs to a broad diverse phylogenetic group of organisms associated with these canyons, sharing common concerns with that group with respect to vulnerability and conservation. This study also advocates that the giant squid can serve as an indicator of effects of ecosystem stress resulting from anthropogenic effects including ocean acidification and warming. It is also shown to be vulnerable to such anthropogenic effects as fishing, acoustic seismic exploration and, possibly, pollutants.

Organic-walled dinoflagellate cysts as indicators of oceanographic conditions and terrigenous input in the NW African upwelling region

In order to examine the spatial distribution of organic-walled dinoflagellate cysts (dinocysts) in recent sediments related to environmental conditions in the water column, thirty-two surface sediment samples from the NW African upwelling region (20–32°N) were investigated. Relative abundances of the dinocyst species show distinct regional differences allowing the separation of four hydrographic regimes. (1) In the area off Cape Ghir, which is characterized by most seasonal upwelling and river discharge, Lingulodinium machaerophorum strongly dominates the associations which are additionally characterized by cysts of Gymnodinium nolleri, cysts of Polykrikos kofoidii and cysts of Polykrikos schwartzii. (2) Off Cape Yubi, a region with increasing perennial upwelling, L. machaerophorum, Brigantedinium spp., species of the genus Impagidinium and cysts of Protoperidinium stellatum occur in highest relative abundances. (3) In coastal samples between Cape Ghir and Cape Yubi, Gymnodinium catenatum, species of the genus Impagidinium, Nematosphaeropsis labyrinthus, Operculodinium centrocarpum, cysts of P. stellatum and Selenopemphix nephroides determine the species composition. (4) Off Cape Blanc, where upwelling prevails perennially, and at offshore sites, heterotrophic dinocyst species show highest relative abundances. A Redundancy Analysis reveals fluvial mud, sea-surface temperature and the depth of the mixed layer in boreal spring (spring) as the most important parameters relating to the dinocyst species association. Dinocyst accumulation rates were calculated for a subset of samples using well-constrained sedimentation rates. Highest accumulation rates with up to almost 80,000 cysts cm − 2 ka − 1 were found off Cape Ghir and Cape Yubi reflecting their eutrophic upwelling filaments. A Redundancy Analysis gives evidence that primary productivity and the input of fluvial mud are mostly related to the dinocyst association. By means of accumulation rate data, quantitative cyst production of individual species can be considered independently from the rest of the association, allowing autecological interpretations. We show that a combined interpretation of relative abundances and accumulation rates of dinocysts can lead to a better understanding of the productivity conditions off NW Africa.

Diatom stratigraphy of the late Pleistocene (Brunhes) subarctic Pacific

Three piston cores in the subarctic region of the North Pacific show consistent changes in relative abundance of diatom species throughout the Brunhes magnetic epoch. These events can be used both as stratigraphic markers to subdivide the interval and as indicators of oceanographic conditions. The stratigraphic record shows an acme for A. ochotensis from about 625-350 Kyr (Isotope Stages 15-10); a marked increase in amplitude of abundance fluctuations for R. hebetata 300-0 Kyr (Stages 8-1), the extinction of R. curvirostris at 276 Kyr (Stage 8), and abundance fluctuations of D. seminae roughly in phase with the global oxygen isotope record from 450-0 Kyr (Stages 12-1). In the subarctic Pacific, an abrupt change in species abundance is not a reliable indicator of hiatus occurrence. Although details are not clear, there appears to have been a fundamental change of the subarctic gyre during the middle Brunhes (Stages 10-8 time), with more intense glacial intervals and stronger glacial—interglacial contrast occurring after that time. Coarse clastic detritus is not restricted to glacial intervals, suggesting that ice-rafting has occurred throughout the Brunhes interval; peak levels of ice-rafting may occur during ice-growth and decay, as well as during short intervals within a stage.

Breeding Patterns of Galápagos Penguins as an Indicator of Oceanographic Conditions

Surface water changes associated with El Niño have been known to affect deleteriously top carnivores along coastal South America. Data on the breeding strategies of Galápagos penguins and other seabirds indicate that the biological effects of El Niño extend much farther west. The breeding biology of these seabirds is adapted to frequent changes in productivity which are associated with El Niño.