Resilience of estuarine phytoplankton and their temporal variability along salinity gradients during drought and hypersalinity

Nche-Fambo, Fru Azinwi; Scharler, Ursula M.; Tirok, Katrin

doi:10.1016/j.ecss.2015.03.011

Cited by 39 publications

(34 citation statements)

References 54 publications

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“…Obtained results give strong evidence that elevated salinities (42)(43)(44)(45)(46)(47)(48)(49)(50)(51), in synergy with high water temperatures (26-30 • C), directly affect the condition, reproductive investment, and consequently the reproductive potential of mature female E. fimbriata. For the first time in clupeid fishes, the current study shows a spawning optimum at salinities that far exceeded marine conditions.…”

Section: Discussionmentioning

confidence: 80%

“…In specimens sampled inside the estuary seasonal differences in K became apparent with notable peaks in February (cool and dry season) and July (warm and dry season). This may hint towards a shift from a marine to a hypersaline phytoplankton community, and thus to temporal differences in food item quality/abundance [49,50]. Also, females spawning in the estuary's middle reaches were exhibiting lower condition indices (K hyd ) (1.37 ± 0.08) than the ones reproducing in the open ocean (1.56 ± 0.12).…”

Section: Discussionmentioning

confidence: 96%

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Ethmalosa fimbriata (Bowdich 1825), a Clupeid Fish That Exhibits Elevated Batch Fecundity in Hypersaline Waters

Döring

Tiedemann

Stäbler

et al. 2017

Fishes

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Abstract:Little is known about the concerted influence of temperature and salinity on the fecundity of clupeid fishes. Due to a globally changing climate, both physical parameters might act as stressors, severely affecting the reproductive potential of clupeid fish populations inhabiting tropical estuaries. Differences in relative batch fecundities, the gonado-somatic index, and the condition index of bonga shad (Ethmalosa fimbriata) were analysed in individual females sampled at the Senegalese coast and inside the inverse Sine Saloum estuary, where salinity increases upstream in all seasons. Multiple linear regression models on fecundity and gonadal energy storage show that clupeids can adapt towards increasing their reproductive investment at temperatures (26-30 • C) and salinities (42-51), which by far exceed marine conditions, in an effort to maximize recruitment success. This reproductive strategy, however, is accompanied by a trade-off between reproductive effort and somatic growth, which ultimately limits the species' reproductive potential inside the estuary. The observed high variability in batch fecundities might be a viable mechanism to adjust to fluctuating and rather extreme environmental conditions. Understanding the spawning biology of exploited clupeid fishes in drastically changing environments is crucial for evaluating the reproductive potential of stocks at the outer reach of their physiological performance curve.

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Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 96%

Ethmalosa fimbriata (Bowdich 1825), a Clupeid Fish That Exhibits Elevated Batch Fecundity in Hypersaline Waters

Döring

Tiedemann

Stäbler

et al. 2017

Fishes

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“…If the generally accepted underestimation of phytoplankton species richness using microscopy [58] is also assumed, it is obvious the actual number of phytoplankton taxa must be noticeably higher in the GRE. Phytoplankton richness in the GRE can be comparable to that of other estuaries describing 97 taxa (belonging to a total of 44 genera) in the Schelde Estuary [59], 45 genera in South Africa St. Lucia Estuary [60], 55 genera in the Kowie Estuary [61] and those indicating the presence of 63 genera following a molecular approach in the Vire River Estuary [62]. A similar molecular approach detected up to 101 genera in the Segura river estuary [63].…”

Section: Discussionmentioning

confidence: 88%

Seston fatty acids to quantify phytoplankton functional groups and their spatiotemporal dynamics in a highly turbid estuary

Cañavate

Bergeijk

González‐Ortegón

et al. 2019

Preprint

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Phytoplankton community composition expresses estuarine functionality and its assessment can be improved by implementing novel quantitative fatty acid based procedures. Fatty acids have similar potential to pigments for quantifying phytoplankton functional groups but have been far less applied. A recently created dataset containing vast information on fatty acids of phytoplankton taxonomic groups was used as reference to quantify phytoplankton functional groups in the yet undescribed Guadalquivir River Estuary. Twelve phytoplankton groups were quantitatively distinguished by iterative matrix factor analysis of seston fatty acid signatures in this turbid estuary. Those phytoplankton groups including species unfeasible for microscopy identification (coccoid or microflagellated cells) could be quantified when using fatty acids. Conducting monthly matrix factor analyses over a period of two years and the full salinity range of the estuary indicated that diatoms dominated about half of the phytoplankton community spatiotemporally. The abundance of Cyanobacteria and Chlorophytes was inversely related to salinity and little affected by seasonality. Euglenophytes were also more abundant at lower salinity, increasing their presence in autumn-winter. Coccolithophores and Dinophytes contributed more to phytoplankton community at higher salinity and remained little affected by seasonality. Multivariate canonical analysis indicated that the structure of the estuarine phytoplankton community was most influenced by salinity, secondly influenced by water temperature, irradiance and river flow, and unaffected by nutrients. Fatty acids are especially suited for phytoplankton community research in high turbid estuaries and generate outcomes in synergy with those derived from classical pigment assessments.

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“…fimbriata mainly feeds on diatoms and dinoflagellates (Bainbridge 1961, Blay & Eyeson 1982a, but literature on phytoplankton community composition in tropical hypersaline environments is scarce. The most dominant taxa under hypersaline conditions in a South African estuary were cyanobacteria, although a resilience to high salinities was also detected in diatoms (Nche-Fambo et al 2015). The trophic marker for a diatom-based diet 16:1 (n-7) indeed constituted rather large averages in all examined oocytes (Dalsgaard et al 2003).…”

Section: Discussionmentioning

confidence: 99%

“…This is probably caused by a decrease in enzymatic activity due to lower oxygen availability and the need to maintain cell membrane stability at higher temperatures (Hixson & Arts 2016). Also, phytoplankton community composition changes under hypersaline conditions, as found in inverse estuaries (Nche-Fambo et al 2015). Therefore, water temperature and salinity are suspected to have direct effects on the FA composition in food items relevant for E. fimbriata (Bainbridge 1961, Blay & Eyeson 1982a.…”

Section: Introductionmentioning

confidence: 99%

Using oocyte essential fatty acid composition to assess spawner reproductive potential under hypersaline conditions

Döring¹,

Ekau²

2017

Mar. Ecol. Prog. Ser.

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Inversion of estuaries in the dry tropics (i.e. salinity increases upstream) against the backdrop of a globally changing climate is forcing migratory clupeid fish species to adapt quickly to modifications in their spawning habitats to ensure reproductive success. Hatching success and survival probabilities of marine fish eggs and early life stages are prone to impairment under high temperature and elevated salinity conditions. Essential fatty acids affect osmoregulation in marine fish early life stages, and deficiencies can therefore be expected to cause elevated offspring mortality under hyperosmotic conditions, ultimately modifying a stock's reproductive potential. Here we show that oocytes spawned by bonga shad Ethmalosa fimbriata inside a hypersaline estuary exhibited significantly higher 20:4 (n-6) proportions (1.6 ± 0.7% of total fatty acids) than oocytes spawned under marine conditions (0.6 ± 0.2%). Further, oocyte proportions in 20:4 (n-6), 20:5 (n-3), and 20:6 (n-3) were positively correlated with water temperature, water salinity, and female reproductive investment (relative batch fecundity, gonado-somatic index, oocyte dry weight). Oocytes spawned during high temperature/high salinity conditions inside the estuary are therefore likely to develop normally under the prevailing conditions. Reproductive potential was determined to be highest in females spawning inside the estuary at the end of the wet season, when temperatures are high and salinities are less stressful due to freshwater input. Results lead to the conclusion that migratory clupeid fishes can maintain their reproductive potential in hypersaline estuaries and lagoons, which potentially allows for sustainable stock sizes.

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Resilience of estuarine phytoplankton and their temporal variability along salinity gradients during drought and hypersalinity

Cited by 39 publications

References 54 publications

Ethmalosa fimbriata (Bowdich 1825), a Clupeid Fish That Exhibits Elevated Batch Fecundity in Hypersaline Waters

Ethmalosa fimbriata (Bowdich 1825), a Clupeid Fish That Exhibits Elevated Batch Fecundity in Hypersaline Waters

Seston fatty acids to quantify phytoplankton functional groups and their spatiotemporal dynamics in a highly turbid estuary

Using oocyte essential fatty acid composition to assess spawner reproductive potential under hypersaline conditions

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