Osmotic regulation and the evolution of brackish- and fresh-water faunas

Croghan, P. C.

doi:10.1144/gsjgs.140.1.0039

Cited by 23 publications

(6 citation statements)

References 24 publications

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“…Marginal-marine environments, including environments in which IHS is developed (e.g., estuarine channels, delta distributaries), characteristically display steep salinity gradients resulting from variations in: 1) the amount of freshwater input from rivers and runoff from land; 2) tidal range; 3) rain fall; 4) evaporation; 5) salinity content in adjacent open-ocean coastal waters, 6) morphology of the coastal area; and, 7) differences in wind direction and velocity (Dorjes and Howard, 1975;. Salinity gradients produce a physiologically stressful environment for many groups of organisms, and are only tolerated by organisms with specialized adaptations for regulating their cellular chemistry under fluctuating, and decreased, salinity concentrations (Croghan, 1983;. In general, decreasing salinity results in decreasing species diversity.…”

Section: Brackish-water Modelmentioning

confidence: 99%

Seasonal Controls On the Development And Character of Inclined Heterolithic Stratification In A Tide-Influenced, Fluvially Dominated Channel: Fraser River, Canada

Sisulak¹,

Dashtgard²

2012

Journal of Sedimentary Research

104

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Section: Brackish-water Modelmentioning

confidence: 99%

Seasonal Controls On the Development And Character of Inclined Heterolithic Stratification In A Tide-Influenced, Fluvially Dominated Channel: Fraser River, Canada

Sisulak¹,

Dashtgard²

2012

Journal of Sedimentary Research

104

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“…Settings characterized by reduced and/or fluctuating salinity show a pronounced size reduction of fauna compared to fully marine counterparts (Milne, 1940). This appears, in part, to be a response to the physiological difficulties in ionic regulation and osmo-regulation (Croghan, 1983). Further, the rigors of inhabiting brackish water imposes an increased oxygen requirement on the fauna, which is minimized by small body sizes (Remane and Schlieper, 1971).…”

Section: Salinity Changes-mentioning

confidence: 99%

Ichnology of Deltas: Organism Responses to the Dynamic Interplay of Rivers, Waves, Storms, and Tides

MacEachern¹,

Bann²,

Bhattacharya³

et al. 2005

River Deltas-Concepts, Models, and Examples

200

246

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Analyses of deltaic facies successions highlight recurring ichnological patterns that reflect a variety of physicochemical stresses imposed upon infaunal organisms by the interaction of various delta-front processes. Analysis of numerous ancient deltaic deposits in Canada, the United States, Australia, and offshore Norway persistently show reductions in bioturbation intensity and impoverishment in ichnological diversity, compared to those of nondeltaic shorelines. Some facies locally demonstrate sporadic colonization and recolonization of substrates left denuded by episodic depositional conditions. Deltaic ichnological suites also locally display size reductions of ichnogenera and a paucity of suspension-feeding ethologies. Resulting trace-fossil suites are overwhelmingly dominated by depositfeeding behaviors, even in sandy facies. Such ichnological characteristics largely reflect increased sedimentation rates and heightened fluvial discharge, which serve to impede infaunal colonization. River-derived stresses are profound: salinity changes, hypopycnal-flow-induced water turbidity, distributary flood discharges with accompanying phytodetrital (comminuted plant debris) pulses, hyperpycnal-flow-induced sediment gravity flows, and fluid-mud deposition all conspire to produce the overall depauperate nature of the ichnological assemblage. Freshet-discharge events during river floods, accompanied by hyperpycnal conditions, may lead to the episodic introduction of reduced-salinity waters immediately above the sediment-water interface in delta-front and prodelta depositional settings. Such conditions may facilitate development of synaeresis cracks and promote reductions in infaunal populations. Wave energy generally buffers fluvial effects, by dispersing suspended sediment offshore and encouraging the thorough mixing of waters of contrasting salinity. High mud concentrations near the delta front damp wave energy, however, limiting its effectiveness in remediating the benthic ecosystem, particularly immediately following distributary flood discharges and storm events. In wavedominated settings, strong alongshore drift also operates to extend river-derived stresses considerable distances downdrift from distributary mouths. Where asymmetric deltas are formed, markedly different ichnological expressions are expressed on either side of distributary-channel mouths. Updrift settings typically retain classic shoreface assemblages, whereas downdrift environments commonly acquire markedly stressed suites. Storm energy may be effective in dispersing mud and mixing waters, but it also results in erosion and episodic sediment deposition. Concomitant precipitation induces river floods, returning river-derived stresses to the delta front. Tidal energy and its effects on the infaunal communities of deltas are poorly documented. Tidal flux may trap mud plumes against the delta front, elevating water turbidity. Pronounced mud flocculation coupled with increased settling velocity associated with tidal mixing also leads to rapid deposition ...

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“…Both trends are broadly ascribed to animal-energy expenditure due to osmoregulation (Kinne, 1967;Croghan, 1983;Mantel, 1985;Ferraris et al, 1994;Gingras et al, 1999). Diminution and diversity reduction may also represent the dominance of juvenile over adult forms due to high mortality rates in stressful environments (MacEachern et al, 1999a).…”

Section: Introductionmentioning

confidence: 99%

Brackish-Water Ichnological Trends in a Microtidal Barrier Island-Embayment System, Kouchibouguac National Park, New Brunswick, Canada

Hauck¹,

Dashtgard²,

Pemberton³

et al. 2009

PALAIOS

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A complex variety of marginal-marine microtidal environments from Kouchibouguac Bay, New Brunswick, Canada, present an opportunity to ichnologically and sedimentologically characterize microtidal settings in a high-latitude, temperate subarctic climate. Variations in bioturbate fabrics and distribution of infauna, analysis of the distributions of sediments and physical sedimentary structures, and the distribution of total organic carbon (TOC) can be associated with characteristic depositional processes. From these data typical sedimentary facies associations are produced. In outer estuary tidal inlets and areas of the flood-tidal deltas, strong currents and wave action eradicate the ichnological signature, resulting in variably laminated and bedded sand. In the central estuary, infauna activity coupled with generally low hydraulic energy levels lead to an absence of primary sedimentary structures. The inner estuary near bay-head deltas experiences riverine currents and freshwater influence. As a consequence, primary sedimentary structures are preserved. Mapping of infauna, sediment texture, TOC, and salinity reveals strong links between animal distribution and these three physicochemical parameters. Consequently, the distribution and type of bioturbation observed is at least passively related to grain size, TOC, and salinity. In outer estuaries and lower-central estuaries, salinity is near marine levels and fluctuates minimally. The distribution of infauna in these areas corresponds directly to sediment texture and TOC. Further up the estuaries, lower and fluctuating salinities-in addition to sediment texture and TOC content-control the distribution and diversity of infauna. Mapping of diversity and infaunal size up-estuary reveals two significant trends attributable to salinity stresses: (1) vermiform diminution, and (2) a significant decrease in infaunal diversity.

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Osmotic regulation and the evolution of brackish- and fresh-water faunas

Cited by 23 publications

References 24 publications

Seasonal Controls On the Development And Character of Inclined Heterolithic Stratification In A Tide-Influenced, Fluvially Dominated Channel: Fraser River, Canada

Seasonal Controls On the Development And Character of Inclined Heterolithic Stratification In A Tide-Influenced, Fluvially Dominated Channel: Fraser River, Canada

Ichnology of Deltas: Organism Responses to the Dynamic Interplay of Rivers, Waves, Storms, and Tides

Brackish-Water Ichnological Trends in a Microtidal Barrier Island-Embayment System, Kouchibouguac National Park, New Brunswick, Canada

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