scholarly journals Morphodynamics in a Tropical Shallow Lagoon: Observation and Inferences of Change

2020 ◽  
Author(s):  
Alfred Sunday Alademomi ◽  
Andrew J. Manning ◽  
Victor J. Abbott ◽  
Richard J.S. Whitehouse
Keyword(s):  
Shallow Lagoon

scholarly journals Modeling habitat suitability of the invasive clam Corbicula fluminea in a Neotropical shallow lagoon, southern Brazil

2016 ◽  
Vol 76 (3) ◽  
pp. 718-725
Author(s):  
T. C. L. Silveira ◽  
A. M. S. Gama ◽  
T. P. Alves ◽  
N. F. Fontoura
Keyword(s):  
Organic Matter ◽  
Habitat Suitability ◽  
Organic Matter Content ◽  
Corbicula Fluminea ◽  
Matter Content ◽  
Additive Models ◽  
Sampling Point ◽  
Boosted Regression Tree ◽  
Clam Corbicula ◽  
Shallow Lagoon

Abstract This study aimed to model the habitat suitability for an invasive clam Corbicula fluminea in a coastal shallow lagoon in the southern Neotropical region (–30.22, –50.55). The lagoon (19km2, maximum deep 2.5m) was sampled with an Ekman dredge in an orthogonal matrix comprising 84 points. At each sampling point, were obtained environmental descriptors as depth, organic matter content (OMC), average granulometry (Avgran), and the percentage of sand (Pcsand). Prediction performance of Generalized Linear Models (GLM), Generalized Additive Models (GAM) and Boosted Regression Tree (BRT) were compared. Also, niche overlapping with other native clam species (Castalia martensi, Neocorbicula limosa and Anodontites trapesialis) was examined. A BRT model with 1400 trees was selected as the best model, with cross-validated correlation of 0.82. The relative contributions of predictors were Pcsand-42.6%, OMC-35.8%, Avgran-10.9% and Depth-10.8%. Were identified that C. fluminea occur mainly in sandy sediments with few organic matter, in shallow areas nor by the shore. The PCA showed a wide niche overlap with the native clam species C. martensi, N. limosa and A. trapesialis.

scholarly journals Seychelles Lagoon Provides Corals with a Refuge from Bleaching

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
David Iluz ◽  
Razi Vago ◽  
Nanette E. Chadwick ◽  
Razi Hoffman ◽  
Zvy Dubinsky
Keyword(s):  
Ultraviolet Radiation ◽  
Uv Radiation ◽  
Seawater Temperature ◽  
Uv Absorption ◽  
Bleaching Event ◽  
Laboratory Examination ◽  
Shallow Lagoon

An extensive bleaching event in the summer of the year 1997-1998 affected most reefs along East Africa's shores. In the aftermath of that episode, the reefs of Île Alphonse in the Seychelles were examined and it was found that reefs along the seaward slopes of the island lost >95% of their branching coral colonies, with considerably higher survival of massive species. Île Alphonse features a nearly circular shallow lagoon, with steep seaward slopes. Contrary to our expectations, mortality in the warmer lagoon was far lower than of coral colonies on the surrounding slopes, bathed in deeper and cooler waters. We suggest that corals in the lagoon were protected from UV radiation by leachate stemming from seagrass leaves steeped in the lagoon. Our measurements in the lagoon showed a strong attenuation of ultraviolet radiation, not observed in the waters outside the lagoon, and laboratory examination confirmed that the strong UV absorption of substances leached into seawater from decomposing leaves of the seagrassThalassodendron (=Cymodocea) testudinaceum. Our findings demonstrate the synergism between elevated seawater temperature and UV radiation in triggering bleaching on shallow reefs.

Population structure and trophic composition of the free-living nematodes inhabiting carbonate sands of Davies Reef, Great Barrier Reef, Australia

1986 ◽  
Vol 37 (5) ◽  
pp. 609 ◽  
Author(s):  
DM Alongi
Keyword(s):  
Population Structure ◽  
Great Barrier Reef ◽  
Reef Flat ◽  
Detrended Correspondence Analysis ◽  
Reef Crest ◽  
Barrier Reef ◽  
Back Wall ◽  
Free Living ◽  
Shallow Lagoon ◽  
Reef Zones

Population structure and trophic composition of free-living nematodes from carbonate sands within different functional zones (reef crest, reef flat and lagoon) of Davies Reef in the Great Barrier Reef were examined. At the reef crest (station C) and at a shallow lagoon area unprotected by the back wall of the reef flat (station G), sediments were subjected to intense wave action and supported significantly (P < 0.05) lower mean nematode densities (<60 individuals per 10 cm2) than sands within the other reef zones (100-400 individuals per 10 cm2). Mean nematode densities and numerical species richness were highest (P < 0.05) in a shallow lagoon habitat protected from hydrodynamic- induced disturbances by the back wall of the reef flat (station H). Differences in population densities among the reef zones were not related to water depth or sediment granulometry. Species diversity was low within the reef, with only six species present in deep lagoon sands co-inhabited by actively bioturbating ghost shrimps (Callianassa spp.). Normal classification, nodal analysis and detrended correspondence analysis indicated that faunal groups were distinct among the different reefal zones. Very coarse to medium sands at the reef crest and across the reef flat were inhabited primarily by omnivorous and epistrate-feeding nematodes. Most nematodes within the very fine to fine sands of the lagoon were non-selective or selective deposit feeders. Nematode community structure from the reef crest to the shallow lagoon appears to be determined primarily by sediment granulometry as controlled by reef hydrodynamics, whereas in the deep lagoon nematode communities are negatively affected by the presence of thalassinid ghost shrimps.

scholarly journals Impact of the zebra mussel Dreissena polymorpha invasion on the budget of suspended material in a shallow lagoon ecosystem

2006 ◽  
Vol 60 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Darius Daunys ◽  
Petras Zemlys ◽  
Sergej Olenin ◽  
Anastasija Zaiko ◽  
Christian Ferrarin
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Suspended Material ◽  
Shallow Lagoon
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