Complex and inconsistent patterns of variation in benthos, micro-algae and sediment over multiple spatial scales

Abstract

Because of their close physical relationship, it is often assumed that there are strong functional relationships between sediments and biota. Yet, there have been few studies of the characteristics of sediments over multiple spatial scales, despite evidence that micro-algae and macroand meiofauna vary greatly at cm to km scales. This study quantified variability in macrofauna, micro-algae, and physical and biochemical properties of sediments over scales from 50 cm to km. The benthos was most variable at small scales and, even where there were large mean differences in abundance at large scales, these were small compared to the variation from plot to plot along a shore. Only 1 of 24 analyses showed larger variation at the scale of km than that found at 50 cm. Some measures of microphytobenthos showed large variation at the scale of 100s m or more, but other measures of the same flora did not show similar patterns. Concentrations of sand were consistent at different depths and at large scales, but concentrations of mud were more variable within than among shores. Neither sand nor mud correlated significantly with most biochemical properties of sediments. For sediments, variation at the scale of km was only larger than that of 50 cm in 13 of 57 analyses. To understand the relative importance of ecological processes in determining distributions and abundances, it is important to get quantitative data on the scales at which organisms or habitats vary. These are the scales at which ecological processes are likely to have large effects because large-scale processes are unlikely to explain variation at much smaller scales. The importance of small-scale variability in sediments and the associated biota is discussed in terms of sampling protocols for understanding ecological processes, or for assessing impact or restoration.

Satellite remote sensing reveals a positive impact of living oyster reefs on microalgal biofilm development

“…Fortunately, the high speed of MPB migration allowed us to work with satellite data that could be obtained during most of the low-tide period. It should also be kept in mind that while MPB biomass at the surface of the sediment can change as a result of vertical migration (Brouwer and Stal, 2001;Chennu et al, 2013), it can also be affected by other exogenous factors such as temperature and irradiance (Saburova and Polikarpov, 2003;Jesus et al, 2009;Coelho et al, 2011). A better understanding of these temporal dynamics requires high spatial and temporal resolution RS data.…”

“…MPB biomass is characterized by high heterogeneity occurring on various spatial scales (Chapman et al, 2010). Intra-and interannual MPB variability have previously been assessed on different scales using archived satellite images.…”

Vertical distribution of meiofauna on reflective sandy beaches

“…Diferenças significativas na distribuição vertical dos organismos só foram detectadas quando considerada a menor interação entre os fatores, indicando que a variabilidade entre os pontos dentro de uma mesma praia são responsáveis pela estruturação espacial e vertical dos organismos meiofaunais. (CHAPMAN et al, 2010;VIEIRA;FONSECA, 2013). On sandy beaches, the distribution is primarily controlled by the physical and chemical extremes of interstitial spaces (MCLACHLAN; BROWN, 2006;SCHLACHER et al, 2008).…”

Form, function and physics: the ecology of biogenic stabilisation

“…The result demonstrated the importance of vegetation in reducing wave energy and the resilience of the marsh despite shearing of individual plant elements. This investigation would be difficult in the field, and the results may also be scale-dependant and the outcome may be different if conducted within smaller flumes; indeed, the scale of experiments both spatially and temporally is often an important consideration (Chapman et al 2010). While biofilms are a well-studied phenomenon (Characklis and Marshall 1990), the temporal scale is hardly considered since the majority of studies concern mono-species cultures of medical relevance and focus on molecular interactions at the cell surface in the first hours of settlement as well as infection and antibiotic resistance (e.g.…”