Structure and diversity of intertidal benthic diatom assemblages in contrasting shores: a case study from the Tagus estuary¹

Abstract

The structure of intertidal benthic diatoms assemblages in the Tagus estuary was investigated during a 2-year survey, carried out in six stations with different sediment texture. Nonparametric multivariate analyses were used to characterize spatial and temporal patterns of the assemblages and to link them to the measured environmental variables. In addition, diversity and other features related to community physiognomy, such as size-class or life-form distributions, were used to describe the diatom assemblages. A total of 183 diatom taxa were identified during cell counts and their biovolume was determined. Differences between stations (analysis of similarity (ANOSIM), R = 0.932) were more evident than temporal patterns (R = 0.308) and mud content alone was the environmental variable most correlated to the biotic data (BEST, ρ = 0.863). Mudflat stations were typically colonized by low diversity diatom assemblages (H' ~ 1.9), mainly composed of medium-sized motile epipelic species (250-1,000 μm(3) ), that showed species-specific seasonal blooms (e.g., Navicula gregaria Donkin). Sandy stations had more complex and diverse diatom assemblages (H' ~ 3.2). They were mostly composed by a large set of minute epipsammic species (<250 μm(3) ) that, generally, did not show temporal patterns. The structure of intertidal diatom assemblages was largely defined by the interplay between epipelon and epipsammon, and its diversity was explained within the framework of the Intermediate Disturbance Hypothesis. However, the spatial distribution of epipelic and epipsammic life-forms showed that the definition of both functional groups should not be over-simplified.

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

“…After the oysters were killed, MPB patches regularly showed a more complex and disaggregated structure instead of the regular patch shape usually observed. Variations in bathymetry, tidal dynamics, sediment type, irradiance and grazing had already been documented as factors structuring MPB spatio-temporal distribution (Brotas et al, 1995;Méléder et al, 2003;Sahan et al, 2007;Ribeiro et al, 2013). However, to date there are only a few studies which have explicitly investigated the influence of nearby macrobenthic communities on MPB dynamics (Dame, 1993;Méléder et al, 2003Newell, 2004;Engel et al, 2017).…”

Growth form defines physiological photoprotective capacity in intertidal benthic diatoms

“…TYCHO includes both centric and pennate raphid forms. Intertidal benthic diatom species, but also growth forms, show distinct distribution patterns in time and space, suggesting pronounced (micro)-niche differentiation (Sabbe, 1993;Méléder et al, 2007, Ribeiro et al, 2013. For example, EPM dominates non-cohesive sandy sediments (Méléder et al, 2007), while EPL dominates cohesive muddy sediments (Haubois et al, 2005).…”

“…In temperate seas, intertidal benthic communities are largely dominated by diatoms (Méléder et al, 2007;Ribeiro et al, 2013), which display a high degree of taxonomic, phylogenetic and functional diversity (Kooistra et al, 2007). Several growth forms can be distinguished, which mainly differ in their attachment mode and degree of motility (for a detailed description, see Ribeiro et al, 2013): (1) the epipelon (EPL) comprises larger (usually410 mm) motile diatoms, which can move freely in between sediment particles and typically form biofilms (cf.…”

“…Several growth forms can be distinguished, which mainly differ in their attachment mode and degree of motility (for a detailed description, see Ribeiro et al, 2013): (1) the epipelon (EPL) comprises larger (usually410 mm) motile diatoms, which can move freely in between sediment particles and typically form biofilms (cf. Herlory et al, 2004); (2) the epipsammon (EPM) groups smaller (usuallyo10 mm) diatoms, which live in close association with individual sand grains; and (3) the tychoplankton (TYCHO), which is an ill-defined and rather enigmatic group of largely non-motile diatoms, which presumably have an amphibious life style (both sediment and water column) (for example, Sabbe et al, 2010).…”

Effect of bacteria on growth and biochemical composition of two benthic diatoms Halamphora coffeaeformis and Entomoneis paludosa

“…These two species are usually found in biofilms on intertidal mudflat sediments (Meleder et al, 2007;Ribeiro et al, 2003;Ribeiro et al, 2013). In addition, this study assessed the efficiency of an antibiotic treatment on the bacterial community associated to benthic diatoms.…”