Spatio-temporal changes in microphytobenthos structure analysed by pigment composition in a macrotidal flat (Bourgneuf Bay, France)

Abstract

The aim of this study was to contribute to a better understanding of turbid coastal ecosystems, focusing on spatio-temporal changes at the mesoscale in microphytobenthos structures in a macrotidal bay (Bourgneuf, France). This was based on pigment analysis by high-pressure liquid chromatography (HPLC), reinforced by microscopy observations, in relation to sediment characteristics. Microphytobenthos assemblages of this mudflat were 97% dominated by diatoms, confirmed by HPLC analysis, which showed biomarker pigments of this group: chlorophyll c, fucoxanthin, diadinoxanthin and diatoxanthin. The main assemblage is constituted of epipsammic species, like Plagiogrammopsis, Achnanthes and Cocconeis, characterising mixed sediments. However, this could be replaced by epipelic species, like Plagiotropis, Pleurosigma and Staurophora, during summer due to station silting. Microphytobenthic photosynthetic active biomass in the first 2 mm varied spatially and temporally from 12.2 to 186.9 mg chl a m -2. The predominance of a biomass spatial variability reflected spatial changes in sediment grain size and water content. Biomass in the first 2 mm represented from 28 to 68% of the total amount in the first 10 mm. This indicated an accumulation of biomass in illuminated layers and a biomass decrease with depth associated with increasing values of the ratio of phaeopigments a and fucoxanthin to chlorophyll a (phaeo a/chl a and fuco/chl a). Both could exceed 1.00 in deeper layers. Temporal changes in microphytobenthos structure at the mesoscale were mainly linked to hydrodynamism. This is stronger in winter and responsible for allochthonous pigment input (lutein and phaeophytin b) and sediment mixing, as grazing activity by macro-and meiofauna, forming chlorophyll a breakdown products, is responsible for an increase in fuco/chl a and phaeo a/chl a values during spring/summer. KEY WORDS: Microphytobenthos · Diatoms · Pigments · High-pressure liquid chromatography · HPLC · GranulometryResale or republication not permitted without written consent of the publisher

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

“…An inflection in the reflectance slope is visible around 632 nm, attributable to the absorption by both chl a and chl c, a pigments association specific to diatoms (Méléder et al, 2005). The most striking feature is however the trough at 675 nm associated with chl a absorption, and the resulting reflectance shift between 675 and 700 nm, generally referred to as the NIR/red edge (Gons et al, 2002).…”

Comparative Study on Microphytobenthic Pigments and Total Microbial Biomass by ATP in Intertidal Sediments

“…해수 중 식물플랑크톤 변동은 겨울철에 매우 낮은 농도를 보이는 반면, 저서미세 조류는 겨울철에 높은 생산량을 보인다 (Colijn and de Jonge 1984;de Jonge and Colijn 1994). 저서미세조류는 광합성을 하기 위해 퇴적물 내에서 빛 투과 한계점인 표 층 약 2~4 mm 상층부에서 주로 서식하며 (Colijin 1982;MacIntyre and Cullen 1995), 운동성을 가진 epipelic algae의 활발한 수직 회유와 물리적인 공극수 흐름 (hydrodynamic forces), 그리고 생물교란 등에 의해서 퇴 적물 깊이 10 cm 이하의 깊이에서도 저서미세조류의 존재 가 확인되고 있다 (Cadée and Hegeman 1974;Montani et al 2003;Méléder et al 2005).…”

Downward trophic shift during breeding migration in the shorebird Calidris mauri (western sandpiper)

“…A total of 24 sediment cores (~10 cm depth, 11 cm 2 surface area), covered with biofilm, water, and associated macro-and meiofauna, were frozen in situ by addition of liquid nitrogen (Méléder et al 2005) at low tide on 23, 26 and 30 April 2004. All cores were obtained from muddy sediment within 100 m of the high-water mark.…”

“…Benthic diatoms were separated from the upper 5 mm layer of 1 m 2 of sediment with visible dense biofilm covering as per Decottignies et al (2007). It is likely that the entire active diatom biomass was included in this samples, since it is confined to the upper 2 mm (Méléder et al 2005). Seawater was collected in 15 l plastic containers.…”

“…The taxonomic (to genus level) composition of the microphytic fraction of surface sediment and of western sandpiper stomach contents at the Roberts Bank stopover were determined after separation and processing for light and scanning electron microscopy. The upper 2 mm (photic zone) of the 6 sediment cores and the stomach contents of 3 birds were treated using the Ludox HS40 protocol to observe microalgae (Méléder et al 2005), especially diatoms, and mounted for light photomicrography, using an Olympus AX70 microscope. The same samples of sediment and stomach contents were also processed for scanning electron microscopy (Cannuel & Beninger 2006), and observed using a JEOL JSM 6400F scanning electron microscope.…”