Role of current and prey odour in the displacement behaviour of the sea star Asterias vulgaris

2004 ◽  
Vol 82 (10) ◽  
pp. 1547-1553 ◽  
Author(s):  
David Drolet ◽  
John H Himmelman
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Sea Star ◽  
Sea Stars ◽  
Essential Condition ◽  
Asterias Vulgaris ◽  
Degree Of Orientation ◽  
Slow Moving ◽  
Odour Plumes

We performed a factorial experiment to investigate the effects of current and prey odours (mussels) on the displacement behaviour of the sea star Asterias vulgaris (Verrill, 1866). This sea star is a common subtidal predator of sessile and slow-moving animals in the western North Atlantic Ocean. In the presence of current and prey odours in a flume, sea stars oriented themselves upstream and 70% succeeded in finding the prey. Also, the degree of orientation toward the prey increased as the sea star approached the prey. In contrast, only 5% of individuals tested in still water found the prey. Thus, for A. vulgaris the presence of macroscale flow is an essential condition for locating distant prey. Sea stars tested in current alone showed rheotactic behaviour, moving diagonally upstream. This behaviour should enhance the probability of encountering prey odour plumes in the field. Sea stars moved faster and straighter in flowing water than in still water. The slow movement of A. vulgaris in still water probably minimizes costs of foraging when there is a low chance of finding prey and the straight diagonal movement in current should ensure that the sea star continuously samples new areas, rather than resampling the same odour-free area.

The Role of Aerosols in the Evolution of Tropical North Atlantic Ocean Temperature Anomalies

Science ◽  
2009 ◽  
Vol 324 (5928) ◽  
pp. 778-781 ◽  
Author(s):  
A. T. Evan ◽  
D. J. Vimont ◽  
A. K. Heidinger ◽  
J. P. Kossin ◽  
R. Bennartz
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ocean Temperature ◽  
Temperature Anomalies ◽  
Tropical North Atlantic

Green Sahara Megaperiods during the Pliocene: What was the role of North Atlantic Ocean temperature?

2020 ◽  
Author(s):  
Paul Wilson ◽  
Amy Jewell ◽  
Anya Crocker ◽  
Solana Buchanan ◽  
Bryce Mitsunaga ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Saharan Dust ◽  
The North ◽  
Sst Variability ◽  
Scan Data ◽  
Sahel Region ◽  
Strong Control

<p>The Sahel region is one of the most vulnerable regions on Earth to anthropogenically-driven climate change, but also one of the least equipped to deal with the consequences. Predictions of precipitation levels over the forthcoming centuries diverge, not only in magnitude, but also in the sign of change. One key aspect of this uncertainty comes from the role of Atlantic Ocean sea surface temperatures (SST), which are known to exert a strong control over precipitation in the Sahel and are implicated in both the major drought of the late 20<sup>th</sup> century and extreme droughts associated with the Heinrich events of the last glacial. To better understand how Sahelian hydroclimate may respond to SST variability in a warmer world, we turn to the Pliocene epoch, when atmospheric CO<sub>2</sub> levels were comparable to present.</p><p> </p><p>We studied sediments from Ocean Drilling Project Site 659, which is situated in the subtropical North Atlantic beneath the major modern summer Saharan dust plume. Our new dust accumulation rates and X-ray fluorescence core scan data indicate that there were major shifts between highly arid conditions and humid intervals with vegetated or “Green Sahara” conditions over much of northern Africa, driven by both solar insolation and glacial-interglacial variability. We also report three unusually long Plio-Pliocene humid intervals (each lasting ca. 100 kyr) characterised by very low dust emissions, that we term “Green Sahara Megaperiods (GSMPs)”. All three of these GSMPs occur at times when insolation variability was weak, resulting in values close to the long-term mean. This observation strongly suggests that factors other than insolation drove the sustained humidity of GSMPs. We present paired alkenone SST estimates and multi-species planktonic foramaniferal isotope records from 3.5–2.3 Myr ago to explore the extent to which the GSMPs were accompanied by intervals of extended warmth in the surface waters of the North Atlantic Ocean.</p>

scholarly journals On the generation and role of eddy variability in the central North Atlantic Ocean

1994 ◽  
Vol 99 (C10) ◽  
pp. 20381 ◽  
Author(s):  
Aike Beckmann ◽  
Claus W. Böning ◽  
Bernd Brügge ◽  
Detlef Stammer
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean

scholarly journals Reproductive biology and energetics of the brooding sea star Anasterias antarctica (Echinodermata: Asteroidea) in the Beagle Channel, Tierra del Fuego, Argentina

2017 ◽  
Vol 65 (1-1) ◽  
pp. 221 ◽  
Author(s):  
Analía F. Pérez ◽  
Cintia Fraysse ◽  
Claudia C. Boy ◽  
Lucia Epherra ◽  
Calcagno Javier
Keyword(s):  
Tierra Del Fuego ◽  
Sea Star ◽  
Reproductive Condition ◽  
Sea Stars ◽  
Pyloric Caeca ◽  
Beagle Channel ◽  
Brooding Period ◽  
Wet Weight ◽  
Sexually Mature

The brooding sea star Anasterias antarctica is distributed from the coast of Patagonia to the northern Peninsula of Antarctica. In the Beagle Channel, the females of A. antarctica brood their eggs for seven months and do not feed during this period. The endoparasite Dendrogaster argentinensis (Crustacea: Ascothoracica) causes castration in several species of Anasterias. We randomly collected four samplings of adults in May, August and October (brooding period) and January (non-brooding period). The gonad (GI) and pyloric caeca index (PCI) were calculated as organ wet weight (g) x 100/total wet weight (g). Each individual was sexed by microscopic examination of the gonads. Sex ratio, brooding females/non-brooding females and mature females/non-mature females ratios was 1:1. The male GI reached maximum values in January, when most individuals were sexually mature. The GI of non-brooding females reached its maximum during October when it was significantly higher than those from brooding females. The PCI was minimum in October, being lower in brooding females (August and October). During the non-brooding period, mature females had a significantly higher GI than non-mature females. The PCI did not vary neither between males, nor between mature and non mature females. By the end of the brooding period, non-brooding females showed a higher GI than the brooding females. This is explained by proliferation and increase of the oocytes size of non-brooding females. Mature females showed an incremented GI with presence of mature oocytes, while non-mature females exhibited more abundance of previtelogenic oocytes. Males showed synchronicity in reproductive condition. The females that have not brooded presented a process of active gametogenesis, reaching the summer with a high GI, therefore becoming mature females. Females that had brooded were probably lacking energy for new gonadal maturation. The pyloric caeca would be performing the role of a reserve organ in the brooding females, decreasing its size during the brooding period. Prevalence of D. argentinensis in A. antarctica was 11.06%. As this parasite was recorded in sea stars lacking gonads, these infected hosts could have been castrated. Rev. Biol. Trop. 65(Suppl. 1): S221-S232. Epub 2017 November 01. 

scholarly journals C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

2015 ◽  
Vol 12 (12) ◽  
pp. 9275-9305
Author(s):  
A. Singh ◽  
S. E. Baer ◽  
U. Riebesell ◽  
A. C. Martiny ◽  
M. W. Lomas
Keyword(s):  
Time Series ◽  
Organic Matter ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Euphotic Zone ◽  
Redfield Ratio ◽  
The North ◽  
Elemental Stoichiometry ◽  
Series Study

Abstract. Nitrogen (N) and phosphorus (P) availability determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio in inorganic nutrients is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation of stoichiometric relationships. We have analysed elemental stoichiometry in the suspended POM and total (POM + DOM) organic matter (TOM) pools in the upper 100 m, and in the exported POM and sub-euphotic zone (100–500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N : P ratios in the TOM pool were more than twice that in the POM pool. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield Ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield Ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry with that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that the variation elemental ratios with depth in the euphotic zone was mainly due to different growth rates of cyanobacterial cells. These time-series data have also allowed us to examine the potential role of climate variability on C : N : P stoichiometry. This study strengthens our understanding of elemental stoichiometry in different organic matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry.

On the key role of nutrient data to constrain a coupled physical–biogeochemical assimilative model of the North Atlantic Ocean

2009 ◽  
Vol 75 (1-2) ◽  
pp. 100-115 ◽  
Author(s):  
Yann Ourmières ◽  
Pierre Brasseur ◽  
Marina Lévy ◽  
Jean-Michel Brankart ◽  
Jacques Verron
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
The North ◽  
The North Atlantic ◽  
Nutrient Data
Sign in / Sign up

Export Citation Format

Share Document