Day–night variation of intertidal flat sediment properties in relation to sediment stability

Friend, Patrick L.; Collins, M.B.; Holligan, P. M.

doi:10.1016/s0272-7714(03)00178-1

Cited by 39 publications

(26 citation statements)

References 36 publications

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“…It is becoming increasingly clear, however, that the relationship between carbohydrates and erosion parameters is highly complex. Friend et al (2003) found a decrease in colloidal carbohydrate at night, but an increase in erosion threshold, a pattern opposite to that expected. They suggested that this may be caused by changing chemical composition of the carbohydrate.…”

Section: Implications Of Differencescontrasting

confidence: 79%

“…Previous studies (Friend et al, 2003(Friend et al, , 2005 showed that surface chlorophyll a tended to be less at night than during the day. Whilst the trend in the current study tended to be the same (4 of 5 comparisons showed a night time decrease in chlorophyll a), the difference between day and night was generally small or not significant.…”

Section: Day and Night Differencesmentioning

confidence: 88%

“…Previous studies have shown that the biochemical properties of intertidal sediments in European estuaries can vary significantly between day and night (Thornton et al, 1999;Ottosen et al, 2001;de Brouwer & Stal, 2001Friend et al, 2003Friend et al, , 2005. Diatoms are known to migrate below the sediment surface in response to tides and light Consalvey et al, 2004) and the production of extracellular polymeric substances (EPS, primarily consisting of carbohydrates) has been shown to be light dependent (de Winder et al, 1999;Taylor et al, 1999;Staats et al, 2000;de Brouwer & Stal, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Weak diurnal changes in the biochemical properties and benthic macrofauna of urbanised mangrove forests and mudflats

Tolhurst

2009

Hydrobiologia

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Diurnal changes in the biochemical properties and the benthic macrofaunal assemblage of sediments in urbanised mangrove forests and their adjacent mudflats in Sydney Harbour were investigated. Behavioural and physiological changes in the microphytobenthos between day and night were predicted to cause diurnal changes in the micro-scale depth distribution of chlorophylls a and b and colloidal carbohydrate. In addition, because macrofauna can alter sediment properties, diurnal changes in the macrofaunal assemblages were investigated. The microphytobenthos at the study sites were predominantly filamentous green algae, although diatoms were present. Samples for biochemical analysis were collected from the top 2 mm of sediment using mini-cryolanders, during low tide in the day and at night. Three biochemical properties of the sediments were measured spectrophotometrically: chlorophylls a and b (surrogate for microphytobenthos biomass) and colloidal carbohydrate. The amount of chlorophylls tended to be less at night than during the day, but site to site variability was large and these differences were generally small and not significant. Depth profiles indicated that there was some redistribution of pigments in the surface 2 mm between day and night, possibly due to migration of microphytobenthos or physiological changes. There was no significant difference in chlorophylls between the mangrove forest and adjacent mudflat, with the exception of chlorophyll b at one sampling time, which was larger in the mangrove forest than on the mudflat. Colloidal carbohydrate was significantly larger in the mangrove forest and significantly less on the mudflat during the day at one site at one time, but otherwise showed no significant differences between day and night or between the mangrove forest and mudflat. Whilst there were some differences in the benthic macrofaunal assemblages between day and night, these differences were only significant for spionids and polychaetes at one time. There were, however, significant differences in assemblages of benthic macrofauna between the mangrove forest and mudflat, probably due to structural differences between these habitats such as the presence of pneumatophores, shade and leaf litter. In summary, there was some minor diurnal variation in the measured biochemical properties of the sediment, but not in the macrofaunal assemblage. Diurnal changes should, therefore, be considered when investigating biochemical properties in these habitats, but they are not a major influence. These findings contrast to previous studies on diatom dominated mudflats in Europe, where stronger diurnal changes in biochemical properties were found. Diurnal changes in the macrofauna assemblages were largely insignificant and therefore could not explain the changes in the biochemical properties. Diurnal effects on the macrofauna in these habitats are more likely to be via altered behaviours and this requires further investigation

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Section: Implications Of Differencescontrasting

confidence: 79%

Section: Day and Night Differencesmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Weak diurnal changes in the biochemical properties and benthic macrofauna of urbanised mangrove forests and mudflats

Tolhurst

2009

Hydrobiologia

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“…The chl a and EPS contents of the surface sediments within Z. noltii beds in Sylt (Table 1) were similar to those recorded by Friend et al (2003a) in Z. noltii beds in the Ria Formosa, Portugal (chl a = 18.1 to 45.1 µg g -1 dry wt; EPS = 332 to 854 µg g -1 dry wt). Friend et al (2003b) also reported a significant correlation between the critical erosion threshold (measured using a Cohesive Strength Meter) and chl a and EPS for a range of habitats and sediment types, with the lowest values associated with bare sandy sediments.…”

Section: Discussionmentioning

confidence: 89%

Effects of seagrass beds (Zostera noltii and Z. marina) on near-bed hydrodynamics and sediment resuspension

Widdows¹,

Pope²,

Brinsley³

et al. 2008

Mar. Ecol. Prog. Ser.

105

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The main objectives of this flume study were to (1) quantify density dependent effects of the short-leaf seagrass Zostera nolti on hydrodynamics and sediment resuspension from a sandy bed, and (2) measure the erodability of 2 contrasting sediments (sandy and muddy) and the extent to which this is modified by the presence of 2 seagrass species, Z. noltii (sandy) and Z. marina (muddy). Field measurements of near-bed tidal currents, turbulence and suspended particulate matter at 2 different Z. noltii locations (low energy [sheltered] and higher energy [exposed] environments) were interpreted in the context of the flume results. Skimming flow above the high density bed of Z. noltii was accompanied by a 40% reduction in near-bed flow, but this was offset by a 2-fold increase in turbulent kinetic energy (TKE) and bed shear stress (τ 0 ). Despite this increase in τ 0 there was an increase in sediment stabilisation with increasing seagrass density (10-fold increase in critical bed shear stress for erosion [τ e ] from 0.1 [bare sediment] to 1.0 Pa at the highest shoot density). This was largely explained by the increased microphytobenthos abundance (reflected in the higher chlorophyll a and carbohydrate contents) and a lower density of the grazer and bio-destabiliser Hydrobia ulvae. In contrast, the muddy site was more easily eroded (10-fold higher), with Z. marina having little effect on sediment erodability (bare: τ e = 0.05 Pa; Z. marina: τ e = 0.07 Pa). This higher erodability was due to differences in hydrodynamics and the physical/biological properties of the sediment. KEY WORDS: Seagrass beds · Zostera noltii · Zostera marina · Hydrodynamics · Sediment resuspensionResale or republication not permitted without written consent of the publisher

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“…Spatial and temporal replication is an especially important consideration when measuring intertidal cohesive sediment erodibility, due to the huge spatial and temporal variability in the properties controlling erodibility Paterson et al 2000;Defew et al 2002;Defew et al 2003;Friend et al 2003;Tolhurst et al 2003). Small-scale spatial variation in the erodibility of cohesive intertidal sediments can result in significant differences in erosion threshold due to device test section size (Tolhurst et al 2000a, b).…”

Section: Introductionmentioning

confidence: 99%

The effects of tidally-driven temporal variation on measuring intertidal cohesive sediment erosion threshold

et al. 2005

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Accurate measurement of intertidal sediment erodibility is essential for the development of meaningful and accurate models of sediment dynamics. Despite considerable advances in technology and methodology, the measurement of cohesive intertidal sediment erosion remains problematic. Sediment erodibility varies according to both physical and biological properties and processes. These cannot be considered in isolation, as they can interact to create both positive and negative feedbacks, resulting in seemingly idiosyncratic responses in the system. If working models of estuarine sediment dynamics are to be made, it is essential that the influence of these processes on both the measurements and the system itself be considered. Recent developments in measurement technology enable rapid measurement of sediment stability allowing temporal and spatial variability to be measured on a time scale of minutes. This paper reports temporal variability in cohesive intertidal sediment erosion threshold related to immersion and emersion, and the concomitant responses in selected sediment properties (carbohydrates, water content and chlorophyll). Erosion threshold tended to increase over emersion and decrease over immersion, although the patterns of change varied depending upon local conditions, and in one case there was no temporal trend. Temporal changes resulted in a range of measured erosion threshold, dependant upon the erosion device used. Modifications to existing methodology, in order to account for this variation, are proposed and implications for modelling erosion processes are considered.

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Day–night variation of intertidal flat sediment properties in relation to sediment stability

Cited by 39 publications

References 36 publications

Weak diurnal changes in the biochemical properties and benthic macrofauna of urbanised mangrove forests and mudflats

Weak diurnal changes in the biochemical properties and benthic macrofauna of urbanised mangrove forests and mudflats

Effects of seagrass beds (Zostera noltii and Z. marina) on near-bed hydrodynamics and sediment resuspension

The effects of tidally-driven temporal variation on measuring intertidal cohesive sediment erosion threshold

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