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Eutrophication plays a crucial role in coastal systems, driving changes in the composition and abundance of flora and fauna with consequent effects for the entire ecosystem. Sensitive to nutrient levels, micro-and macroalgal blooms serve as valuable indicators of eutrophication. The San Antonio Bay (Northern Argentinean Patagonia, 40°43′ S, 64°56′ W) provides an appropriate system to study in situ eutrophication processes on coastal communities. In a multiscale approach, using two different kind of settlement substrates (micro: polyethylene terephthalate, and macro: ceramic), the present study followed benthic algal dynamics over one year, distinguishing changes in natural succession and seasonality. Strong differences were found in the biofilm assemblages after three days, marked by tube dwelling diatoms and Cocconeis spp. under high nutrient-grazer conditions and needle like diatoms (e.g. Nitzschia spp., Tabularia spp.) under lower nutrient-grazer loads. The succession continued by the colonization of macroalgae, with a higher recruitment rate in the nutrient and grazer rich environment with a concomitant higher diversity. Our results show that under higher nutrientgrazer conditions natural benthic succession not only differs in trajectory but in its final taxa composition promoting higher biodiversity and biomass accumulation. In addition, taxa specific substrate preferences interfere with the observed eutrophication pattern, suggesting substrate dependant interrelations between the bloom forming taxa. These findings provide evidence that nutrient enrichment can not only affect an established assemblage but also affect the early succession stages, changing the succession trajectory and thus the final assemblage.

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Understanding the variables (biotic or abiotic) controlling coastal communities is the main goal of ecology research and it is crucial to predict how communities will evolve under the increasing pressure on coastal systems by human activities. The general aims of this study were to assess the variables affecting the distribution of the fast-growing sponge Hymeniacidon cf. perlevis, and to evaluate if physical stressful conditions have an influence in the relationship between Hymeniacidon and the sea lettuce Ulva lactuca. Specifically, the aims were to evaluate the abundance patterns of Hymeniacidon and Ulva and to assess the relationship of Ulva and physical variables on the abundance of Hymeniacidon at both intertidal and subtidal. Hymeniacidon and Ulva showed opposite abundance patterns. Hymeniacidon was more abundant in sites without Ulva, and negatively correlated with Ulva abundance at both heights. Intertidal Hymeniacidon abundance was not correlated with physical variables, but subtidal Hymeniacidon was.

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Here, we describe four new species of Crellidae Dendy, 1922 and discuss characters and relationships from published molecular phylogenies including crellid sponges. New species proposed are Crella (Pytheas) chiloensis Fernandez, Gastaldi, Pardo & Hajdu, sp. nov., from southern Chile (15 m depth), C. (P.) desventuradae Fernandez, Gastaldi, Zapata-Hernández & Hajdu, sp. nov., from Desventuradas Archipelago (10–20 m depth), Crella (P.) santacruzae Fernandez, Gastaldi, Thompson & Hajdu, sp. nov., from deep waters off Argentina (750 m depth) and Crellomima sigmatifera Fernandez, Gastaldi & Hajdu, sp. nov., from the Chilean fjords region (ca. 20 m depth). These new species are set apart from each other and from known species mainly due to aspects of their spiculation. Chelae microscleres and acanthostyles supply characters that might be used to infer phylogenetic relationships and to verify the monophyly of Crella Gray, 1867 and Crellidae, which has seemingly been contradicted by preliminary molecular data available in the systematics’ literature. Our own interpretation of phylogenetic affinities, in the light of morphological characters from previous taxonomic studies, argues for a classification reassessment of materials (vouchers) included in these molecular phylogenies, especially in the case of Crella incrustans (Carter, 1885). We argue that currently available molecular phylogenetic outcomes for crellid sponges are not supportive of the polyphyly of Crella and Crellidae.