Variations in Seasonal Phytoplankton Assemblages as a Response to Environmental Changes in the Surface Waters of Minicoy Island, Lakshadweep

In Mediterranean lagoons, macrophytes often surpass phytoplankton as the most important primary producers. Less frequently, phytoplankton dominates throughout the year, thus knowledge of its dynamics is relatively limited and scattered. In this study, we assessed over two years the dynamics of phytoplankton assemblages, including potential harmful algal species (HAS), in relation to environmental changes in the phytoplankton-dominated Cabras Lagoon (Sardinia, Italy). The lagoon was characterised by uniform spatial conditions, wide temporal variations in salinity (40 PSU) and high nutrient availability. Phosphorus was highest in summer, possibly recycled within the system, while dissolved inorganic nitrogen increased in winter and spring due to watershed discharge. Chlorophyll a, positively correlated with nutrients and rainfall, showed a typical bimodal pattern with summer-winter blooms. Modifications in phytoplankton composition strongly correlated with extreme weather events, such as intense rainfall. This generated an abrupt salinity decrease that, combined with high nutrient availability, favoured the dominance of Cyanophyceae of reduced cell size, such as Cyanobium and Rhabdoderma species. We suggest that the prolonged and intense dominance of Cyanophyceae, added to other HAS, has a negative impact on the primary economic activities of the lagoon, such as fishery, and generally on the whole lagoon functioning.

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Hydrogeochemsitry of montane springs and their influence on streams in the Cairngorm mountains, Scotland

Hydrology and Earth System Sciences ◽

10.5194/hess-3-409-1999 ◽

1999 ◽

Vol 3 (3) ◽

pp. 409-419 ◽

Cited By ~ 24

Author(s):

C. Soulsby ◽

R. Malcolm ◽

R. Helliwell ◽

R.C. Ferrier

Keyword(s):

High Altitude ◽

Surface Waters ◽

Environmental Changes ◽

Seasonal Pattern ◽

Ionic Composition ◽

Spring Water ◽

Residence Times ◽

Sea Salts ◽

Fractured Bedrock ◽

Catchment Areas

Abstract. Springs are important groundwater discharge points on the high altitude (>800m) plateaux of the Cairngorm mountains, Scotland and form important wetland habitats within what is often a dry, sub-arctic landscape. The hydrogeochemistry of a typical spring in the Allt a'Mharcaidh catchment was examined between 1995-98 in order to characterise its chemical composition, identify the dominant controls on its chemical evolution and estimate groundwater residence time using 18O isotopes. Spring water, sustained by groundwater flow in shallow drift deposits and fractured bedrock, was moderately acidic (mean pH 5.89), with a very low alkalinity (mean 18 μeq l-1) and the ionic composition was dominated by sea-salts derived from atmospheric sources. Geochemical modelling using NETPATH, predicted that the dissolution of plagioclase mainly controls the release of Si, non-marine Na, Ca, K and Al into spring water. Hydrological conditions influenced seasonal variations in spring chemistry, with snowmelt associated with more rapid groundwater flows and lower weathering rates than summer discharges. Downstream of the spring, the chemistry of surface water was fundamentally different as a result of drainage from larger catchment areas, with increased soil and drift cover, and higher evaporation rates. Thus, the hydrogeochemical influence of springs on surface waters appears to be localized. Mean δ18O values in spring water were lower and more damped than those in precipitation. Nevertheless, a sinusoidal seasonal pattern was observed and used to estimate mean residence times of groundwater of around 2 years. Thus, in the high altitude plateau of the Cairngorms, shallow, coarse drift deposits from significant aquifers. At lower altitudes, deeper drift deposits, combined with larger catchment areas, increase mean groundwater residence times to >5 years. At high altitudes, the shallow, permeable nature of the drifts dictates that groundwater is vulnerable to impacts of environmental changes that could be usefully monitored at spring sites.

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Pigment signatures of phytoplankton communities in the Beaufort Sea

Biogeosciences Discussions ◽

10.5194/bgd-11-14489-2014 ◽

2014 ◽

Vol 11 (10) ◽

pp. 14489-14530 ◽

Cited By ~ 4

Author(s):

P. Coupel ◽

A. Matsuoka ◽

D. Ruiz-Pino ◽

M. Gosselin ◽

H. Claustre ◽

...

Keyword(s):

Arctic Ocean ◽

Environmental Changes ◽

Beaufort Sea ◽

Total Carbon ◽

The Arctic ◽

Clustering Methods ◽

Phytoplankton Assemblages ◽

Pigment Analysis ◽

Phytoplankton Communities ◽

The Arctic Ocean

Abstract. Phytoplankton are expected to respond to recent environmental changes of the Arctic Ocean. In terms of bottom-up control, modifying the phytoplankton distribution will ultimately affect the entire food web and carbon export. However, detecting and quantifying change in phytoplankton communities in the Arctic Ocean remains difficult because of the lack of data and the inconsistent identification methods used. Based on pigment and microscopy data sampled in the Beaufort Sea during summer 2009, we optimized the chemotaxonomic tool CHEMTAX for the assessment of phytoplankton community composition in an Arctic setting. The geographical distribution of the main phytoplankton groups was determined with clustering methods. Four phytoplankton assemblages were determined and related to bathymetry, nutrients and light availability. Surface waters across the whole survey region were dominated by prasinophytes and chlorophytes, whereas the subsurface chlorophyll maximum was dominated by the centric diatoms Chaetoceros socialis on the shelf and by two populations of nanoflagellates in the deep basin. Microscopic count showed a high contribution of the heterotrophic dinoflagellates Gymnodinium and Gyrodinium spp. to total carbon biomass, suggesting high grazing activity at this time of the year. However, CHEMTAX was unable to detect these dinoflagellates because they lack peridinin. The inclusion in heterotrophic dinoflagellates of the pigments of their prey potentially leads to incorrect group assignments and some misinterpretation of CHEMTAX. Thanks to the high reproducibility of pigment analysis, our results can serve as a baseline to assess change and spatial or temporal variability in phytoplankton populations.

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The Foraminiferal assemblages across three middle Turonian marl bands and a note on their genesis

Journal of Micropalaeontology ◽

10.1144/jm.8.2.143 ◽

1989 ◽

Vol 8 (2) ◽

pp. 143-148 ◽

Cited By ~ 4

Author(s):

P. N. Leary ◽

D. S. Wray

Keyword(s):

Surface Waters ◽

Large Scale ◽

Volcanic Ash ◽

Environmental Changes ◽

Consistent Pattern ◽

Post Mortem ◽

Foraminiferal Assemblage

Abstract. the changes in the Foraminiferal assemblage across three Middle Turonian marl bands show a consistent pattern, with (a) very similar gross assemblage characteristics from the white chalk below and above the marls containing an approximately 60:40% planktonic:benthonic ratio, greater than 50% non-keeled morphotypes (within the planktonic assemblage) and with infaunal and epifaunal groups well represented but (b) from within the marls the assemblage is dominated by benthonics (30:70% p:b ratio), less than 20% non-keeled morphotypes (within the planktonic assemblage) and a benthonic assemblage dominated by the infaunal groups. Although there is evidence of some dissolution within the marls, with the pitting of the thinner test walls, we propose the changes in the assemblage are not due to large scale post mortem diagenetic process. But are most likely due to environmental changes within the chalk sea, possibly caused by the ephemeral introduction into the surface waters of volcanic ash.

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High resolution paleo-environmental changes during the Sapropel 1 in the North Ionian Sea, central Mediterranean

The Holocene ◽

10.1177/0959683620941095 ◽

2020 ◽

Vol 30 (11) ◽

pp. 1504-1515 ◽

Cited By ~ 1

Author(s):

Helena Checa ◽

Giulia Margaritelli ◽

Leopoldo D Pena ◽

Jaime Frigola ◽

Isabel Cacho ◽

...

Keyword(s):

High Resolution ◽

Water Column ◽

Surface Waters ◽

Environmental Changes ◽

Nutrient Content ◽

Ionian Sea ◽

Central Mediterranean ◽

White Variety ◽

The North ◽

Geochemical Analyses

High-resolution paleoceanographic reconstruction of surface water properties during the most recent Sapropel event (S1) has been carried out by means of quantitative analyses of planktonic foraminiferal assemblages, planktonic foraminiferal oxygen isotopes (δ18O) and XRF elemental data from a 655 m depth core recovered in the North Ionian Sea. The results show that the S1 interval presents two distinctive warm phases (S1a and S1b), separated by a cold interruption event (S1i). High resolution faunal and geochemical analyses allow to identify two sub-phases within S1a interval, the oldest one has similar characteristics to S1b interval while the youngest sub-phase has less stratified surface waters with relatively lower nutrient content. The high abundance of Globigerinoides ruber white variety opposite to the low percentages of Neogloboquadrina pachyderma during the pre-S1 phase suggests that the onset of surface waters stratification occurred prior to the beginning of Sapropel deposition, acting as a pre-conditioning phase. Paleo-productivity proxies indicate that the deposition of S1 initiated after an increase in nutrient content, potentially related to increased fluvial inputs. Based on the integrated ecological interpretation of our records we argue that S1a and S1b are characterized as warm, stratified and nutrient rich surface waters in the Ionian Sea, while proxies related to oxygen content indicate dysoxic deep waters linked to a combination of the high nutrient content and stratified water column. The S1 interruption phase is characterized by the entrance of colder waters that caused mixing of the stratified water column and re-ventilation of the deep dysoxic waters.

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Latitudinal Distributions and Controls of Bacterial Community Composition during the Summer of 2017 in Western Arctic Surface Waters (from the Bering Strait to the Chukchi Borderland)

Scientific Reports ◽

10.1038/s41598-019-53427-4 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Jiyoung Lee ◽

Sung-Ho Kang ◽

Eun Jin Yang ◽

Alison M. Macdonald ◽

Hyoung Min Joo ◽

...

Keyword(s):

Bacterial Community ◽

Arctic Ocean ◽

Community Composition ◽

Surface Waters ◽

Bacterial Communities ◽

Environmental Changes ◽

Bacterial Community Composition ◽

Bering Strait ◽

Western Arctic ◽

Chukchi Borderland

AbstractThe western Arctic Ocean is experiencing some of the most rapid environmental changes in the Arctic. However, little is known about the microbial community response to these changes. Employing observations from the summer of 2017, this study investigated latitudinal variations in bacterial community composition in surface waters between the Bering Strait and Chukchi Borderland and the factors driving the changes. Results indicate three distinctive communities. Southern Chukchi bacterial communities are associated with nutrient rich conditions, including genera such as Sulfitobacter, whereas the northern Chukchi bacterial community is dominated by SAR clades, Flavobacterium, Paraglaciecola, and Polaribacter genera associated with low nutrients and sea ice conditions. The frontal region, located on the boundary between the southern and northern Chukchi, is a transition zone with intermediate physical and biogeochemical properties; however, bacterial communities differed markedly from those found to the north and south. In the transition zone, Sphingomonas, with as yet undetermined ecological characteristics, are relatively abundant. Latitudinal distributions in bacterial community composition are mainly attributed to physical and biogeochemical characteristics, suggesting that these communities are susceptible to Arctic environmental changes. These findings provide a foundation to improve understanding of bacterial community variations in response to a rapidly changing Arctic Ocean.

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First record of straight-needle pteropod Creseis acicula Rang, 1828 bloom in the Çanakkale Strait (NE Aegean Sea, Turkey)

Oceanological and Hydrobiological Studies ◽

10.2478/oandhs-2021-0026 ◽

2021 ◽

Vol 50 (3) ◽

pp. 310-324

Author(s):

Sezginer Tunçer ◽

Nazik Öğretmen ◽

Fikret Çakır ◽

Alkan Öztekin ◽

Ayhan Oral ◽

...

Keyword(s):

Surface Waters ◽

Elevated Temperatures ◽

Environmental Changes ◽

Aegean Sea ◽

First Record ◽

Sea Surface ◽

Anthropogenic Activity ◽

Coastal Zones ◽

Straight Needle ◽

Auxiliary Factor

Abstract Pteropods are marine pelagic calcifier mollusks sensitive to chemical changes in seawater due to their highly soluble aragonite shells. Increased acidity (reduced pH) of seawater causes difficulties in precipitating their shells and/or results in their dissolution, which is related to increased atmospheric CO2 concentrations and warming of seawater. They are therefore indicators of environmental changes. In this paper, we present the first record of the straight-needle pteropod Creseis acicula Rang, 1828 bloom in the surface waters of the Ҫanakkale Strait, Turkey (NE Aegean Sea), encountered in July 2020, when the highest sea surface temperatures and pH levels since 2007 were recorded. In coastal zones, such as the Ҫanakkale Strait, anthropogenic activity contributes significantly to environmental changes. Consequently, the increase in pH at elevated temperatures indicates an auxiliary factor (i.e. anthropogenic activity) that triggered the C. acicula bloom, rather than global atmospheric CO2 levels.

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Cell Size Dependent Responses of Phytoplankton Assemblages to Nitrate and Phosphate Additions in Surface Waters of the Northern South China Sea

Open Journal of Marine Science ◽

10.4236/ojms.2014.42008 ◽

2014 ◽

Vol 04 (02) ◽

pp. 61-67 ◽

Cited By ~ 1

Author(s):

Rong Yi ◽

Yehui Tan ◽

Shengfu Wang ◽

Pingping Shen ◽

Zhixin Ke ◽

...

Keyword(s):

South China Sea ◽

Cell Size ◽

South China ◽

Surface Waters ◽

Northern South China Sea ◽

Phytoplankton Assemblages ◽

China Sea ◽

Size Dependent

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Distribution and Control of Bacterial Community Composition in Marian Cove Surface Waters, King George Island, Antarctica during the Summer of 2018

Microorganisms ◽

10.3390/microorganisms8081115 ◽

2020 ◽

Vol 8 (8) ◽

pp. 1115

Author(s):

Soyeon Kim ◽

Ju-Hyoung Kim ◽

Jae-Hyun Lim ◽

Jin-Hyun Jeong ◽

Jang-Mu Heo ◽

...

Keyword(s):

Bacterial Community ◽

Spatial Variation ◽

Community Composition ◽

Surface Waters ◽

Bacterial Communities ◽

Environmental Changes ◽

Bacterial Community Composition ◽

Environmental Parameters ◽

And Control ◽

The Antarctic

Marian Cove is experiencing some of the most rapid environmental changes in the Antarctic region; however, little is known about the response of bacterial communities to these changes. The main purpose of this study was to investigate the spatial variation of physical–biogeochemical–bacterial community features in the Marian Cove surface waters and the environmental parameters governing the spatial variation in the bacterial community composition during the summer of 2018. The Marian Cove surface waters are largely composed of two different characteristics of water masses: relatively low-temperature, -salinity, and -nutrient surface glacier water (named SGW) and relatively high-temperature, -salinity, and -nutrient surface Maxwell Bay water (named SMBW). The SGW bacterial communities were dominated by unclassified Cryomorphaceae, Sedimenticola, and Salibacter genera, while the SMBW bacterial communities were dominated by Sulfitobacter, Arcobacter, and Odoribacter genera. Spatial variations in bacterial community composition were mainly attributed to physical and biogeochemical characteristics, suggesting that the bacterial community composition of the Marian Cove surface waters is mainly determined by environmental characteristics. These findings provide a foundation to improve the understanding of bacterial community variations in response to a rapidly changing Marian Cove in the Antarctic.

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