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Intertidal soft sediment microphytobenthic biofilms are often dominated by diatoms, which are able to regulate their photosynthesis by physiological processes (e.g. down-regulation through the xanthophyll cycle, referred to as non-photochemical quenching, NPQ) and behavioural processes (e.g. vertical cell movement in the sediment -biofilm matrix). This study investigated these 2 processes over a 6 h emersion period using chemical inhibitors under 2 light treatments (ambient and constant light at 300 µmol m -2 s -1). Latrunculin A (Lat A) was used to inhibit cell movement and dithiothreitol (DTT) to inhibit NPQ. HPLC analysis for chlorophyll a and spectral analysis (Normalised Difference Vegetation Index) indicated that Lat A significantly inhibited cell movement. Photosynthetic activity was measured using variable chlorophyll fluorescence and radiolabelled carbon uptake and showed that the non-migratory, Lat A-treated biofilms were severely inhibited as a result of the high accumulated light dose (significantly reduced maximum relative electron transport rate, rETR max , and light utilisation coefficient, α, compared to the migratory DTT and control-treated biofilms). No significant patterns were observed for 14 C data, although a decrease in uptake rate was observed over the measurement period. NPQ was investigated using HPLC analysis of xanthophyll pigments (diatoxanthin and the percentage de-epoxidation of diadinoxanthin), chlorophyll fluorescence (change in maximum fluorescence yield) and the 2nd order spectral derivative index (diatoxanthin index). Patterns between methods varied, but overall data indicated greater NPQ induction in the non-migratory Lat A treatment and little or no NPQ induction in the DTT and control treatments. Overall, the data resulted in 2 main conclusions: (1) the primary response to accumulated light dose was vertical movement, which when inhibited resulted in severe down-regulation/photoinhibition; (2) diatoms down-regulated their photosynthetic activity in response to accumulated light dose (e.g. over an emersion period) using a combination of vertical migration and physiological mechanisms that may contribute to diel and/or tidal patterns in productivity.KEY WORDS: Benthic · Diatom · Down-regulation · Migration · Photophysiology · ProductivityResale or republication not permitted without written consent of the publisher

The present study evaluated some cryoprotectants and concentrations for curimba (Prochilodus lineatus) semen preservation from a simple methodology of analysis of sperm morphology. Semen of nine males was diluted (1:4) into eight cryosolutions, all of them containing 5% of BTS™ Minitüb, still comprising methanol or dimethyl sulphoxide (DMSO) at four concentrations: 5%, 7.5%, 10% and 12.5%. Morphological sperm analysis was performed on an optical microscope at × 1000 magnification. Damages on the head, midpiece and tail rest (the main and terminal portions) were investigated and classified as primary or secondary, according to the assumed influence on fertilization. There was a linear reduction in the total damages with an increase in the cryoprotectant concentration. Samples with DMSO showed the lowest percentage of fractured tails and tail stumps. The cryopreservation protocol retained the fertilizing potential of the sperm after freezing and both methanol 5% and DMSO 7.5% conferred adequate protection to the curimba sperm cells. Sperm morphology, as pointed out here, must be incorporated into routine fish sperm (cryopreserved or not) analysis once sperm defects influence fertilization directly. To the best of our knowledge, this was the first report on curimba sperm damages after cryopreservation by optical microscopy. The classification model presented in this study can be adequate to tackle fish sperm damages.

Haslea ostrearia is a common marine tychopelagic diatom which has the particularity of synthesizing a blue-green hydrosoluble pigment called "marennine". This pigment, when released into the external medium, is known to be responsible for the colour of oyster gills. Here we present results for main biophysical and biochemical characteristics of pure intra-and extracellular marennine. Tests for chemical determination show that the nature of the two forms of marennine cannot be distinguished and could be related to a polyphenolic compound. Nevertheless, based on spectral properties and the molecular weight, which is about 10751 ± 1 and 9893 ± 1 Da, for the intracellular and extracellular forms respectively, we assess that the pigment accumulated in the apex of the cell and the one released in the external medium have probably distinct molecular structures.

Spatiotemporal changes in microphytobenthos species composition were investigated in relation to structural variables—biomass; life‐forms; detritus ratio, pheopigment a (pheo a):chl a; and sediment characteristics—at mesoscale in a shellfish macrotidal ecosystem. To characterize algae assemblages, multivariate analyses were performed (multidimensional scaling [MDS] ordination and clustering), supported by correlations between structural variables. Microphytobenthos, dominated by 97% diatoms belonging to 89 taxa, was constituted by two main assemblages: The first one, composed of common species (occurrence >50%), mainly nanobenthic (size <30 μm) and epipsammic (sand‐fixed cells), was associated with mixed sediments. The major species contributing to this assemblage were Navicula perminuta, Achnanthes hauckiana, Fallacia tenera, A. lanceolata var. elleptica, Amphora spp., Plagiogrammopsis vanheurkii, and Plagiogramma tenuissimum (see Table 2 for taxonomic authors). Species diversity was high (N1∼ 11), often linked to high biomass values (>70 mg chl a · m−2) and low detritus ratio. Conversely, the second assemblage comprised occasional species (occurrence from 10% to 50%), mainly microbenthic (>30 μm) and epipelic (moving cells), occurring during summer at muddy sites. This assemblage, characterized by low diversity, high biomass variability, and high detritus ratio, was dominated by Scolioneis tumida or Plagiotropis vitrea and Navicula spartinetensis. Whereas hydrodynamics globally explained the gradual assemblage changes throughout the entire mudflat and the year, oyster beds and ridge and runnel features appeared to be local spatial structuring factors allowing the establishment of specific assemblages. This study suggests a significant role for epipsammon biomass, until now underestimated, in the functioning of this turbid coastal ecosystem. Microphytobenthic taxa identified from samples from the first 2 mm of sediment from Bourgneuf Bay (France) mudflat between May 2000 and July 2001. Taxa Abbreviation Ecologya Size Occurrence (%) Common species  Plagiogrammopsis vanheurkii (Grunow) Hasle, Stosch et SyvertsenPlagp vanhEpipsammicNanobenthic82.50  Amphora spp.Amph spp.EpipsammicNanobenthic81.25  Achnanthes hauckiana GrunowAchn haucEpipsammicNanobenthic78.75  Navicula perminuta GrunowNavi permEpipelicNanobenthic76.25  Thalassiosira decipiens (Grunow) Jörg.Thal deciEpipsammicNanobenthic76.25  Fallacia tenera (Hust.) D. G. MannFall teneEpipelicNanobenthic73.75  Achnanthes lanceolata var. elleptica CleveAchn lancEpipsammicNanobenthic71.25  Cymatosira belgica GrunowCyma belgEpipsammicNanobenthic68.75  Navicula spartinetensis M. J. Sullivan et ReimerNavi sparEpipelicNanobenthic68.75  Plagiogramma tenuissimum Hust.Plagg tenuEpipsammicNanobenthic66.25  Cocconeis hoffmanni SimonsenCocc hoffEpipsammicNanobenthic65.00  Biremis ambigua D. G. MannBire ambiEpipsammicNanobenthic58.75  Odontella aurita (Lyngb.) C. AgardhOdon auriEpiphyticMicrobenthic57.50  Navicula anglica RalfsNavi anglEpipelicNanobenthic56.25  Cocconeis scute...

The diatom Haslea ostrearia that lives in oyster ponds has the distinctive feature of synthesizing "marennine", a blue-green pigment of which the chemical nature still remains unknown. This pigment is responsible for the greening of oyster gills. Here, we report a new method for extraction and purification of intracellular (accumulated in the apex of the cell) and extracellular (released into the external medium) forms of the pigment. Intracellular marennine is obtained by extraction from blue algal pellets with a carbonate buffer. The extract is then centrifuged and filtered. Extracellular marennine is obtained by clarification of blue-coloured culture medium. Both extracts are then purified by a semi-preparative process, using ultrafiltration through membranes and anion-exchange chromatography. This procedure allows us to produce native pigment displaying the degree of purity required to enter upon the molecular characterisation of marennine. By this process, about 35% of the initial amount of pigment can be recovered. If necessary, this method could be easily scaled up to a larger production system to accommodate potential industrial applications.

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