Tidal Stage Changes in Structure and Diversity of Intertidal Benthic Diatom Assemblages: a Case Study from Two Contrasting Charleston Harbor Flats

The interaction between waves, surges and tides is one of the main drivers of coastal total water levels (TWL). &#160;Understanding this interaction is crucial for studying high TWL formation near shore, and to do this it is important to not only evaluate how high the TWL is but also when and where it occurs.In this study we use a high resolution (1.5 km) three-way coupled (waves-atmosphere-ocean) numerical model developed by the MetOffice (UKC4) to study coastal conditions at the UK coast during the extreme events of winter 2013, which was chosen as case study because of the amount of flooding that occurred in relation to storms and surges during this period.For each coastal grid point the ten strongest storms of that winter, ranked by the significant wave height (Hs) magnitude, were selected. During these storm periods, the number of hours in which Hs and surges exceeded the 90th percentile of winter 2013 were evaluated considering what tidal stage they occurred on. The same was done for instances where high Hs and surges occurred simultaneously. The aim is to understand if specific areas were predominantly affected by one of the TWL components and how Hs and surges interacted with the tide. What was the spatial distribution of the waves, surges, and tides during winter 2013? Did extreme Hs and Surges occur more often over specific stages of the tidal cycle? Did they occur simultaneously?&#160;In this study we show that during the winter 2013, Hs and surges above the 90th percentile value did occur simultaneously at all stages of the tidal cycle. They more often occurred together over the rising tide with in average 8.7% and 8.6% of instances found two and three hours before high tide. In 7.7% of cases high wave and surges also concurred at high tide.

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Paleodepth determination from Antarctic benthic diatom assemblages

Marine Micropaleontology ◽

10.1016/s0377-8398(96)00036-9 ◽

1997 ◽

Vol 29 (3-4) ◽

pp. 301-318 ◽

Cited By ~ 14

Author(s):

Jason M. Whitehead ◽

Andrew McMinn

Keyword(s):

Benthic Diatom ◽

Diatom Assemblages

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Effects of Didymosphenia geminata blooms on benthic diatom assemblages in the Restigouche River Watershed, eastern Canada

Botany ◽

10.1139/cjb-2014-0216 ◽

2015 ◽

Vol 93 (5) ◽

pp. 317-323 ◽

Cited By ~ 4

Author(s):

Branaavan Sivarajah ◽

Joshua Kurek ◽

Kathleen M. Rühland ◽

John P. Smol

Keyword(s):

Benthic Diatom ◽

Diatom Assemblage ◽

Diatom Assemblages ◽

Eastern Canada ◽

Didymosphenia Geminata ◽

Assemblage Composition ◽

River Watershed ◽

And Function ◽

Riverine Systems ◽

The Impact

Nuisance Didymosphenia geminata (Lyngbye) M. Schmidt (didymo) blooms were first reported in 2006 from the Restigouche River Watershed (RRW), eastern Canada. Although government agencies and recreational users are concerned about these blooms, little is known about the impact on biota and (or) the structure and function of the relatively pristine riverine systems of the RRW. Here, we assess whether didymo blooms affect overall benthic diatom assemblage composition by examining epilithic samples from middle stretches of the Patapedia and Upsalquitch rivers. Significant (albeit minor) differences (P < 0.05) in diatom assemblage composition between sites, with and without didymo blooms, were only observed from the Patapedia River. Rarefied diatom species diversity (Hill’s N2) and rarefied richness did not differ significantly among sites, regardless of the presence or absence of blooms. Our data show that didymo blooms have minimal effect on benthic diatom assemblage composition in the RRW.

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Penicillin-mediated changes in viable benthic diatom assemblages – insights about the relevance of bacteria across spatial and seasonal scales

Marine and Freshwater Research ◽

10.1071/mf13083 ◽

2014 ◽

Vol 65 (5) ◽

pp. 437 ◽

Cited By ~ 1

Author(s):

Priya M. D'Costa ◽

Arga C. Anil

Keyword(s):

Ecological Study ◽

Benthic Diatom ◽

Diatom Assemblages ◽

Total Inhibition ◽

Mesocosm Experiments ◽

Lactam Antibiotic ◽

Intertidal Sandflat ◽

Penicillin Treatment ◽

Conditioning Film ◽

Limited Diffusion

Penicillin, a β-lactam antibiotic, cannot affect diatoms directly but does so through bacteria. Its effects on viable benthic diatom assemblages in a tropical environment were evaluated across spatial (intertidal sandflat, mangrove site, port environment) and seasonal (post-monsoon, pre-monsoon, monsoon) scales. Penicillin treatment resulted in bacterial suppression and a reduction in diatoms at the intertidal and mangrove sites having stable pennate-dominated assemblages. Diatom response at the port site, dominated by transient centric diatoms, ranged from total inhibition to enhancement. The monsoon diatom assemblages, which differed in composition from those in other seasons, showed reduced susceptibility to penicillin. These observations highlight the bacterial influence on diatom assemblages and the significance of species composition of diatom assemblages in these interactions. Epipsammic diatoms (Cocconeis, Grammatophora and Thalassionema) were more sensitive to penicillin than epipelic forms, probably due to: (1) their inability to escape unfavourable bacterial metabolites because of limited diffusion in benthic environments; and (2) the interference of penicillin with the bacterial ‘conditioning’ film required for their attachment. Overall, the observations from the present, preliminary, ecological study provide insights into the relevance of bacteria in influencing viable benthic diatom assemblages across spatial and seasonal scales and emphasise the need for future mesocosm experiments on these aspects.

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