Estuarine zooplankton community structure and dynamics

Wooldridge, T.

doi:10.1017/cbo9780511525490.007

Cited by 84 publications

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“…Shifts in the total zooplankton abundances and biomass within southern African estuaries and indeed estuaries 412 worldwide, have been reported to be related to the interactive effects of temperature and food availability [2,5,17] The influence of temperature can largely be discounted as water temperatures were broadly similar during the two seasons The significant increase in zooplankton density and biomass recorded from dry to wet season during this study is, therefore, likely to be the result of elevated food availability. While the dry season biomass and densities values are in the range reported for Kariega Estuary, the wet season densities and biomass are substantially higher and are in the range reported for permanently open southern African estuaries with sustained freshwater inflow [2][3][4]13]. Results of the hierarchical cluster analyses indicated that the wet and dry seasons were characterised by distinct zooplankton communities (Figure 7).…”

Section: Discussionmentioning

confidence: 52%

“…Although the actual abundances of Pseudodiaptomus hessei increased from dry to wet season, the percentage contribution of the total abundance decreased from ≈25% to 15%. Successional patterns of copepods within southern African estuaries are largely driven by alterations in salinity [2]. Acartia longipatella reportedly attains the highest abundances and biomass during periods when oligohaline conditions prevail [2,5,21].…”

Section: Discussionmentioning

confidence: 99%

“…The influence of the reduced freshwater inflow on the biology of southern African estuaries is now well documented [1,2]. Reduced freshwater inflow into estuaries has been linked to a decrease in the phytoplankton size composition and daily production rates largely because freshwater inflow represents the primary source of nutrients necessary to sustain the growth of the phytoplankton, particularly diatoms [1,3,4].…”

Section: Introductionmentioning

confidence: 99%

“…Reduced freshwater inflow into estuaries has been linked to a decrease in the phytoplankton size composition and daily production rates largely because freshwater inflow represents the primary source of nutrients necessary to sustain the growth of the phytoplankton, particularly diatoms [1,3,4]. Among the heterotrophic components of the estuarine food web, the alteration in the riverine inflow into estuaries has been linked to changes in the recruitment, biomass and species composition and distribution of both inverstebrates and vertebrates within these systems [2,5,6]. The formation of horizontal salinity gradients in estuaries is also associated with spatial patterns in the plankton biomass (so-called river-estuary interface (REI) zone [7] Finally, freshwater inflow into estuaries has been linked an increased diversity of niches and food sources available to animals in these systems [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…The hypersaline conditions in the upper reaches of the estuary can be attributed to reduced freshwater inflow as a result of small catchment area (≈680 km 2 ), the presence of several impoundments along the Kariega River and high evaporative losses, particularly during the summer months [12,13]. Localised flooding occurred during September 2006 along the south-east coast of South Africa, resulting in a horizontal salinity gradient being recorded within the system for the first time since 1991.…”

Section: Introductionmentioning

confidence: 99%

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Response of the Plankton to a Fresh Water Pulse in a Fresh Water Deprived, Permanently Open South African Estuary

Froneman¹,

Vorwerk²

2013

JWARP

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This study assessed the influence of a freshwater pulse on selected physico-chemical and biological variables in a permanently open freshwater deprived southern African estuary. In the absence of the freshwater pulse a reverse gradient in salinity was evident with hypersaline (salinity > 40) conditions prevailing in the upper reaches of the estuary. Total chlorophyll-a (chl-a) concentration during this period ranged from 0.25 to 0.60 µg·l (SD ± 1203) and the biomass 21.8 mg·dwt·m −3 (SD ± 196). The total zooplankton abundance during the dry season was numerically dominated by the copepod nauplii and the calanoid copepod, Pseudodiaptomus hessei, which contributed up to 76% of the total zooplankton counts. The freshwater pulse was associated with the establishment of a horizontal gradient in salinity along the length of the estuary and a significant increase in the total chl-a concentration (range from 0.74 to 11.75 µg·l −1) and zooplankton biomass (range from 23.7 to 76.6 mg·dwt·m −3 ) (p < 0.05 in both cases). Additionally, there was a marked increase in the total zooplankton abundances and biomass within the estuary. A distinct shift in the zooplankton community composition was evident with the copepod, Acartia longipatella numerically dominating the zooplankton counts.

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Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Response of the Plankton to a Fresh Water Pulse in a Fresh Water Deprived, Permanently Open South African Estuary

Froneman¹,

Vorwerk²

2013

JWARP

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The response of two South African east coast estuaries to altered river flow regimes

Grange

Whitfield²,

Villiers

et al. 2000

Aquatic Conserv: Mar. Freshw. Ecosyst.

100

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1. Major reductions in catchment run‐off, a result of frequent and prolonged drought conditions, together with extensive impoundment of rivers and streams, has led to concern about the possible negative effects on downstream estuaries. Preliminary studies have shown that changes in river flow and associated nutrient inputs have had a predominantly negative impact on the aquatic biota of Eastern Cape estuaries. Natural successions now have human imposed trajectories which are reducing variability and forcing both freshwater ‘deprived’ and freshwater ‘enriched’ systems into artificial cycles. 2. The Kariega and Great Fish estuaries in the Eastern Cape Province are used in a comparative manner to illustrate how differences in riverine inflow can influence the structure and functioning of selected biotic components in permanently open systems. Maximum chlorophyll a values in the freshwater deprived Kariega Estuary were 1 μg L−1, whereas maximum values in the freshwater enriched Great Fish Estuary were 22 μg L−1. Mean zooplankton biomass in the lower, middle and upper reaches of the Kariega Estuary was always below 50 mg m−3, whereas in the same reaches of the Great Fish Estuary, these values ranged from 256 to 4253 mg m−3. Similarly, mean ichthyonekton densities in the mouth region of the Kariega Estuary were 49 individuals per 100 m2 compared with 279 per 100 m2 in the Great Fish Estuary. 3. Temporal changes of riverine flow reinforce the importance of allochthonous inputs to the functioning of Eastern Cape estuaries. A comparison between a dry and wet period in the Kariega Estuary revealed mean nitrate and phosphate concentrations increasing from 5 to 101 μmol L−1 and from 1 to 5 μmol L−1, respectively. Phytoplankton stocks responded positively to freshettes in both the Kariega and Great Fish estuaries. Similarly, peaks in zooplankton biomass in the Great Fish Estuary increased rapidly in response to high food resource availability resulting from elevated river discharge. The higher ichthyoplankton and ichthyonekton densities in the Great Fish Estuary, when compared with the Kariega Estuary, were attributed to a combination of stronger olfactory cues for larval immigrants from the sea and elevated food stocks in the former system. Copyright © 2000 John Wiley & Sons, Ltd.

show abstract

The response of two South African east coast estuaries to altered river flow regimes

Grange

Whitfield²,

Villiers

et al. 2000

Aquatic Conserv: Mar. Freshw. Ecosyst.

View full text Add to dashboard Cite

1. Major reductions in catchment run-off, a result of frequent and prolonged drought conditions, together with extensive impoundment of rivers and streams, has led to concern about the possible negative effects on downstream estuaries. Preliminary studies have shown that changes in river flow and associated nutrient inputs have had a predominantly negative impact on the aquatic biota of Eastern Cape estuaries. Natural successions now have human imposed trajectories which are reducing variability and forcing both freshwater 'deprived' and freshwater 'enriched' systems into artificial cycles.2. The Kariega and Great Fish estuaries in the Eastern Cape Province are used in a comparative manner to illustrate how differences in riverine inflow can influence the structure and functioning of selected biotic components in permanently open systems. Maximum chlorophyll a values in the freshwater deprived Kariega Estuary were 1 mg L − 1 , whereas maximum values in the freshwater enriched Great Fish Estuary were 22 mg L − 1 . Mean zooplankton biomass in the lower, middle and upper reaches of the Kariega Estuary was always below 50 mg m − 3 , whereas in the same reaches of the Great Fish Estuary, these values ranged from 256 to 4253 mg m − 3 . Similarly, mean ichthyonekton densities in the mouth region of the Kariega Estuary were 49 individuals per 100 m 2 compared with 279 per 100 m 2 in the Great Fish Estuary.3. Temporal changes of riverine flow reinforce the importance of allochthonous inputs to the functioning of Eastern Cape estuaries. A comparison between a dry and wet period in the Kariega Estuary revealed mean nitrate and phosphate concentrations increasing from 5 to 101 mmol L − 1 and from 1 to 5 mmol L − 1 , respectively. Phytoplankton stocks responded positively to freshettes in both the Kariega and Great Fish estuaries. Similarly, peaks in zooplankton biomass in the Great Fish Estuary increased rapidly in response to high food resource availability resulting from elevated river discharge. The higher ichthyoplankton and ichthyonekton densities in the Great Fish Estuary, when compared with the Kariega Estuary, were attributed to a combination of stronger olfactory cues for larval immigrants from the sea and elevated food stocks in the former system.

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Estuarine zooplankton community structure and dynamics

Cited by 84 publications

References 0 publications

Response of the Plankton to a Fresh Water Pulse in a Fresh Water Deprived, Permanently Open South African Estuary

Response of the Plankton to a Fresh Water Pulse in a Fresh Water Deprived, Permanently Open South African Estuary

The response of two South African east coast estuaries to altered river flow regimes

The response of two South African east coast estuaries to altered river flow regimes

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