Geographic and environmental factors affecting the distribution of kelp beds and barren grounds and changes in biota associated with kelp reduction at sites along the Norwegian coast

1997 ◽  
Vol 54 (12) ◽  
pp. 2872-2887 ◽  
Author(s):  
Knut Sivertsen
Keyword(s):  
Environmental Factors ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
The Arctic ◽  
Laminaria Hyperborea ◽  
Factors Affecting ◽  
Kelp Beds ◽  
The Mean ◽  
Transition Areas ◽  
Barren Grounds

Sites at 244 locations along the west and north Norwegian coasts were investigated to evaluate whether kelp (Laminaria hyperborea) beds had been overgrazed by the sea urchins Strongylocentrotus droebachiensis and Echinus esculentus in the years 1981-1992. Barren ground communities were found in sheltered and moderately wave-exposed areas mainly in the inner and middle archipelago from Nordmøre (63°N) northwards. Densities of large-sized (adult and intermediate) L. hyperborea were 20.7 individuals ·m-2 in kelp beds and 9.7 individuals ·m-2 in transition areas. Juvenile Laminaria spp. were present at densities of 23.9 individuals ·m-2 in kelp beds, 3.6 individuals ·m-2 in transition areas, 0.0 individuals ·m-2 in barren grounds, and 59.1 individuals ·m-2 in kelp-harvested locations. Both the densities and the mean size of S. droebachiensis in barren grounds decreased northwards. The mean densities were 52.2 and 26.1 individuals ·m-2 for the areas south and north of the Arctic Circle, respectively. Multivariate analysis (CANOCO) showed that seven ``environmental'' factors (i.e., kelp depth gradient, distance (latitude), time of sampling, nematode infection in S. droebachiensis, wave exposure, coastal gradient, and substratum) contributed significantly to variability in the distribution of kelp beds and barren grounds. Species in hard-bottom communities in shallow waters could be divided into three distinct BIOTA.

scholarly journals Depletion of coastal predatory fish sub-stocks coincided with the largest sea urchin grazing event observed in the NE Atlantic

AMBIO ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 163-173 ◽  
Author(s):  
Kjell Magnus Norderhaug ◽  
Kjell Nedreaas ◽  
Mats Huserbråten ◽  
Even Moland
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Local Population ◽  
Population Connectivity ◽  
Strongylocentrotus Droebachiensis ◽  
Predatory Fish ◽  
Ne Atlantic ◽  
Laminaria Hyperborea ◽  
Fish Stocks ◽  
Coastal Fisheries

AbstractIn this contribution, we propose fishery driven predator release as the cause for the largest grazing event ever observed in the NE Atlantic. Based on the evolving appreciation of limits to population connectivity, published and previously unpublished data, we discuss whether overfishing caused a grazer bloom of the sea urchin (Strongylocentrotus droebachiensis) resulting in overgrazing of more than 2000 km2 kelp (Laminaria hyperborea) forest along Norwegian and Russian coasts during the 1970 s. We show that coastal fisheries likely depleted predatory coastal fish stocks through modernization of fishing methods and fleet. These fish were important predators on urchins and the reduction coincided with the urchin bloom. From this circumstantial evidence, we hypothesize that coastal predatory fish were important in regulating sea urchins, and that a local population dynamics perspective is necessary in management of coastal ecosystems.

scholarly journals Environmental factors affecting pre-weaning survival of Red Sokoto goats.

2021 ◽  
Vol 32 (2) ◽  
pp. 185-190
Author(s):  
U. K. Oke ◽  
B.B.A. Taiwo ◽  
V. Buvanendran' ◽  
S.A.S. Olorunju ◽  
I.F. Adu
Keyword(s):  
Environmental Factors ◽  
Dry Season ◽  
Animal Production ◽  
Season Of Birth ◽  
Factors Affecting ◽  
Production Research ◽  
The Mean ◽  
One Year ◽  
Birth Type ◽  
Research Institute

Effects of environmental factors viz, hirth year, parity, sex, birth type and season of birth on preweaning survival of Red Sokoto goats (RSG) using production records kept between 1978 - 1985 at the National Animal Production Research Institute (NAPRI), Shika-Zaria were investigated. Birth year, parity and season of birth significantly (P<0.05) affected preweaning survival while birth type and sex of kid did not. The mean survival to weaning at 3 months was 72% and was highest in does with 4 or more parities (77%) and least in primiparous does (66%). Survival was significantly higher during harmattan and worse during the dry season. Losses were more concentrated in the O 7 days of life in primiparous does during the dry season. Overall productivity of does and interac lions between parity and birth cype significantly affected survival. Breeding RSG older than one year to kids preferably during 'harmattan' would improve preweaning survival of the kids.

Atlantic wolffish (Anarhichas lupus L.; Pisces: Anarhichidae) predation on green sea urchins (Strongylocentrotus droebachiensis (O.F. Mull.); Echinodermata: Echinoidea) in eastern Newfoundland

1986 ◽  
Vol 64 (9) ◽  
pp. 1920-1925 ◽  
Author(s):  
D. W. Keats ◽  
D. H. Steele ◽  
G. R. South
Keyword(s):  
Gastrointestinal Tract ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
Rocky Subtidal ◽  
Anarhichas Lupus ◽  
The Mean ◽  
Atlantic Wolffish ◽  
Turn Over

The diet of the Atlantic wolffish was studied by examining the contents of the gastrointestinal tracts of 90 individuals collected from the sea urchin dominated rocky subtidal in eastern Newfoundland. Green sea urchins comprised 75% of the overall diet by weight. Horse mussels ranked second but comprised only 9.5% of the diet. The remainder of the diet consisted of several species of invertebrates and fish. The average (over the whole season) wolffish contained 120 g of urchins, equivalent to the biomass of urchins on 0.23 m2 in the middle of the urchin-dominated zone. During April–September, prior to breeding, the average male wolffish contained 174 g of urchins, and the average female contained 85 g of urchins, biomass values representing, respectively, 0.33 and 0.16 m2. Assuming that the contents of the gastrointestinal tract turn over every 3 days, it was calculated that during May through August each wolffish consumes on average 5.29 kg of urchins (males, 7.09 kg; females, 3.50 kg). Based on these figures, a density of 1 wolffish pair per 20 m2 would be required to consume the mean biomass (532 g m−2) of urchins present in the urchin-dominated zone in 1 year.

Ocean pout (Macrozoarces americanus (Bloch and Schneider) (Pisces: Zoarcidae)) predation on green sea urchins (Strongylocentrotus droebachiensis (O.F. Mull.) (Echinodermata: Echinoidea)) in eastern Newfoundland

1987 ◽  
Vol 65 (6) ◽  
pp. 1515-1521 ◽  
Author(s):  
D. W. Keats ◽  
D. H. Steele ◽  
G. R. South
Keyword(s):  
Gastrointestinal Tract ◽  
Sex Ratio ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
Feeding Period ◽  
Rocky Subtidal ◽  
Green Sea Urchin ◽  
The Mean ◽  
Turn Over

The diet of ocean pout was studied by analysis of the contents of the gastrointestinal tracts of 151 individuals collected from the green sea urchin dominated rocky subtidal in eastern Newfoundland. Green sea urchins constituted 62% of the overall diet by weight. The brittle star, Ophiopholus aculeata, constituted 7% of the diet, while the remainder was miscellaneous invertebrates and fish (mainly capelin and billfish). From April to July, when the fish are inshore and feeding, before breeding, the average ocean pout contained 56.3 g of urchins. This is a biomass of urchins equivalent to that in 0.106 m2 of the middle of the urchin-dominated zone. During the inshore feeding period, the average male ocean pout contained 65.0 g of urchins, and the average female contained 47.5 g, biomass values representing 0.122 and 0.089 m2, respectively. Assuming that the contents of the gastrointestinal tract turn over every 3 days, and assuming a 1:1 sex ratio, it is calculated that while inshore, before a seasonal reduction in feeding associated with the spawning season, each ocean pout consumes on average 2.29 kg of urchins (males 2.64 kg, females 1.93 kg). Based on these figures, a density of one ocean pout pair per 8.6 m2 would be required to completely consume the mean biomass (532 g m−2) of urchins present in the urchin-dominated zone in one season.

scholarly journals Ecological Factors Affecting Student Concentration in Classroom: Students' Viewpoint at Hormozgan University of Medical Sciences

2019 ◽  
Author(s):  
A Marzban ◽  
V Rahmanian ◽  
M Ayasi ◽  
S Delavari ◽  
M Barzegaran
Keyword(s):  
Standard Deviation ◽  
Environmental Factors ◽  
Ecological Factors ◽  
Cross Sectional Study ◽  
Medical Sciences ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Significant Difference ◽  
The Mean ◽  
One Way Anova

Introduction: Environmental factors such as temepertature, humidity and light can affect learning environment and consecuently learning quality. This study aimed to investigate the ecological factors affecting concentration in the classroom from the viewpoints of students of Hormozgan University of Medical Sciences. Methods: This cross-sectional study was conducted on 400 students using stratified random sampling method. The data collection tool was a two-part standard two-part questionnaire of demographic characteristics and ecological factors influencing the concentration including 29 questions. Data were analyzed using SPSS24 software using central scatter indicators (frequency, frequency, mean and standard deviation), independent t-test and one-way ANOVA. Result: The mean and standard deviation of student's score on the ecological factors affecting concentration in the classroom in three areas related to the teacher, the student and the environment were 3.69 ± 1.48, 4.20 ± 1.56 and 3.10 ± 1.54. There was a significant difference between the mean scores of students' opinions about environmental factors in both sexes (P = 0.02). Conclusion: The results showed that, by planning and holding joint meetings between the professors, students and educational officials of Hormozgan University of Medical Sciences, effective steps canbe taken to improve the environmental conditions affecting concentration in the classrooms.

Environmental factors affecting reproducibility of bioremediation field assays in Antarctica

2020 ◽  
Vol 169 ◽  
pp. 102915 ◽  
Author(s):  
L.M. Martínez Álvarez ◽  
L.A.M. Ruberto ◽  
J.M. Gurevich ◽  
W.P. Mac Cormack
Keyword(s):  
Environmental Factors ◽  
Factors Affecting

scholarly journals Enhanced Viral Activity in the Surface Microlayer of the Arctic and Antarctic Oceans

2021 ◽  
Vol 9 (2) ◽  
pp. 317
Author(s):  
Dolors Vaqué ◽  
Julia A. Boras ◽  
Jesús Maria Arrieta ◽  
Susana Agustí ◽  
Carlos M. Duarte ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Food Web ◽  
Physicochemical Characteristics ◽  
The Arctic ◽  
Microbial Food Web ◽  
Surface Microlayer ◽  
Polar Regions ◽  
Nutrient Inputs ◽  
Viral Activity ◽  
The Impact

The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column.

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