Microscale imaging sheds light on species-specific strategies for photo-regulation and photo-acclimation of microphytobenthic diatoms.

Intertidal microphytobenthic (MPB) biofilms are key sites for coastal primary production, predominantly by pennate diatoms exhibiting photo-regulation via non-photochemical quenching (NPQ) and vertical migration. Movement is the main photo-regulation mechanism of motile (epipelic) diatoms and because they can move from light, they show low-light acclimation features such as low NPQ levels, as compared to non-motile (epipsammic) forms. However, most comparisons of MPB species-specific photo-regulation have used low light acclimated monocultures, not mimicking environmental conditions. Here we used variable chlorophyll fluorescence imaging, fluorescent labelling in sediment cores and scanning electron microscopy to compare the movement and NPQ responses to light of four epipelic diatom species from a natural MPB biofilm. The diatoms exhibited different species-specific photo-regulation features and a large NPQ range, exceeding that reported for epipsammic diatoms. This could allow epipelic species to coexist in compacted light niches of MPB communities. We show that diatom cell orientation within MPB can be modulated by light, where diatoms oriented themselves more perpendicular to the sediment surface under high light vs. more parallel under low light, demonstrating behavioural, photo-regulatory response by varying their light absorption cross-section. This highlights the importance of considering species-specific responses and understanding cell orientation and photo-behaviour in MPB research.

Assessing the efficiency of low-cost cleaning methods for diatoms from intertidal sediment samples.

This study aims to compare the effectiveness of several low-cost reagents in obtaining high-quality diatom slides for microphytobenthos research. We evaluated the performance of eight reagents in sediment samples of beach intertidal zones. For each of the tested reagents, different pre-treatment conditions (pre-washed; non-washed) and three different temperatures (room temperature at 26 °C, 60 °C, and 100 °C) were also evaluated. For each treatment (combinations between reagents, temperatures, and pre-treatment conditions), we counted diatoms cells that met the criteria necessary for taxonomic identification (Whole/Half frustules or valves without cell material) in 30 randomly chosen fields of view in definitive preparations made from the treated samples. We also compared the treatments regarding species richness and diversity observed in the definitive preparations. The reagents influenced more the conditions of diatoms cells than the temperature and pre-treatment. H2O2, HNO3, NaClO were the methods that had the best performance in relation to the number of identifiable items. The six treatments with H2O2 presented similar amounts of identifiable items, regardless of pre-treatment and temperature. HNO3 presented a higher number of identifiable items in non-washed and pre-washed treatments at 60 °C and non-washed at 100 °C. NaClO had its best performance the following treatments: non-washed at room temperature and non-washed and pre-washed at 60 °C. H2O2 and HNO3 also showed better results for diatom species richness and diversity, followed by NaClO. The use of H2O2 was more robust since it obtained good results regardless of temperature and pre-treatments and should be preferred. HNO3 and NaClO should be used only with the appropriate temperatures, and pre-washing should be avoided.

Plastics in sea surface waters around the Antarctic Peninsula.

Although marine plastic pollution has been the focus of several studies, there are still many gaps in our understanding of the concentrations, characteristics and impacts of plastics in the oceans. This study aimed to quantify and characterize plastic debris in oceanic surface waters of the Antarctic Peninsula. Sampling was done through surface trawls, and mean debris concentration was estimated at 1,794 items.km-2 with an average weight of 27.8 g.km-2. No statistical difference was found between the amount of mesoplastics (46%) and microplastics (54%). We found hard and flexible fragments, spheres and lines, in nine colors, composed mostly of polyurethane, polyamide, and polyethylene. An oceanographic dispersal model showed that, for at least seven years, sampled plastics likely did not originate from latitudes lower than 58°S. Analysis of epiplastic community diversity revealed bacteria, microalgae, and invertebrate groups adhered to debris. Paint fragments were present at all sampling stations and were approximately 30 times more abundant than plastics. Although paint particles were not included in plastic concentration estimates, we highlight that they could have similar impacts as marine plastics. We call for urgent action to avoid and mitigate plastic and paint fragment inputs to the Southern Ocean.

Photosynthetic epibionts and endobionts of Pacific oyster shells from oyster reefs in rocky versus mudflat shores.

The Pacific oyster, Crassostrea gigas (Thunberg), is the main bivalve species cultivated in the world. With global warming enabling its reproduction and larval survival at higher latitudes, this species is now recognized as invasive and creates wild oyster reefs globally. In this study, the spatial distribution of photosynthetic assemblages colonizing the shells of wild C. gigas was investigated on both a large scale (two contrasting types of reefs found in mudflats and rocky areas) and a small scale (within individual shells) using a hyperspectral imager. The microspatial distribution of all phototrophs was obtained by mapping the Normalized Difference Vegetation Index (NDVI). Second derivative (δδ) analyses of hyperspectral images at 462, 524, 571 and 647 nm were subsequently applied to map diatoms, cyanobacteria, rhodophytes and chlorophytes, respectively. A concomitant pigment analysis was carried out by high performance liquid chromatography and completed by taxonomic observations. This study showed that there was high microalgal diversity associated with wild oyster shells and that there were differences in the structure of the phototropic assemblages depending on the type of reef. Namely, vertically-growing oysters in mudflat areas had a higher biomass of epizoic diatoms (hyperspectral proxy at δδ462 nm) and were mainly colonized by species of the genera Navicula, Nitzschia and Hippodonta, which are epipelic or motile epipsammic. The assemblages on the horizontal oysters contained more tychoplanktonic diatoms (e.g. Thalassiosira pseudonana, T. proschkinae and Plagiogrammopsis vanheurckii). Three species of boring cyanobacteria were observed for both types of reef: Mastigocoleus testarum, Leptolyngbya terrebrans, and Hyella caespistosa, but the second derivative analysis at 524 nm showed a significantly higher biomass for the horizontally-growing oysters. There was no biomass difference for the boring chlorophyte assemblages (δδ647 nm), with two species: Eugomontia testarum and Ostreobium quekettii observed for both types of reef. This study shows that oyster shells are an idiosyncratic but ubiquitous habitat for phototrophic assemblages. The contribution of these assemblages in terms of biomass and production to the functioning of coastal areas, and particularly to shellfish ecosystems, remains to be evaluated.

Contribution of benthic microalgae to the temporal variation in phytoplankton assemblages in a macrotidal system.

Suspended marine benthic microalgae in the water column reflect the close relationship between the benthic and pelagic components of coastal ecosystems. In this study, a 12-year phytoplankton time-series was used to investigate the contribution of benthic microalgae to the pelagic system at a site along the French-Atlantic coast. Furthermore, all taxa identified were allocated into different growth forms in order to study their seasonal patterns. The highest contribution of benthic microalgae was observed during the winter period, reaching up to 60% of the carbon biomass in the water column. The haptobenthic growth form showed the highest contribution in terms of biomass, dominant in the fall-winter period when the turbidity and the river flow were high. The epipelic growth form did not follow any seasonal pattern. The epiphytic diatom Licmophora was most commonly found during summer. As benthic microalgae were found in the water column throughout the year, the temporal variation detected in the structure of pelagic assemblages in a macrotidal ecosystem was partly derived from the differentiated contribution of several benthic growth forms.

Effects of elevated temperature and CO2 on intertidal microphytobenthos.

BACKGROUND: Microphytobenthos (MPB) are the main primary producers of many intertidal and shallow subtidal environments. Although these coastal ecosystems are particularly vulnerable to anthropogenic activities, little is known on the effects of climate change variables on the structure and productivity of MPB communities. In this study, the effects of elevated temperature and CO2 on intertidal MPB biomass, species composition and photosynthetic performance were studied using a flow-through experimental life support system. RESULTS: Elevated temperature had a detrimental effect on MPB biomass and photosynthetic performance under both control and elevated CO2. Furthermore, elevated temperature led to an increase of cyanobacteria and a change in the relative abundance of major benthic diatom species present in the MPB community. The most abundant motile epipelic species Navicula spartinetensis and Gyrosigma acuminatum were in part replaced by tychoplanktonic species (Minidiscus chilensis and Thalassiosira cf. pseudonana) and the motile epipelic Nitzschia cf. aequorea and N. cf. aurariae. Elevated CO2 had a beneficial effect on MPB biomass, but only at the lower temperature. It is possible that elevated CO2 alleviated local depletion of dissolved inorganic carbon resulting from high cell abundance at the sediment photic layer. No significant effect of elevated CO2 was detected on the relative abundance of major groups of microalgae and benthic diatom species. CONCLUSIONS: The interactive effects of elevated temperature and CO2 may have an overall detrimental impact on the structure and productivity of intertidal MPB, and eventually in related ecosystem services.

Structure and diversity of intertidal benthic diatom assemblages in contrasting shores: a case study from the Tagus estuary(1).

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.

Photosynthesis assessment in microphytobenthos using conventional and imaging pulse amplitude modulation fluorometry.

Imaging pulse amplitude modulated (Imaging-PAM) fluorometry is a breakthrough in the study of spatial heterogeneity of photosynthetic assemblages. However, Imaging and conventional PAM uses a different technology, making comparisons between these techniques doubtful. Thereby, photosynthetic processes were comparatively assessed using conventional (Junior PAM and PAM 101) and Imaging-PAM on intertidal microphytobenthos (MPB; mud and sand) and on cork oak leaves. Lower values of α (initial slope of the rETR, relative photosynthetic electron transport rate) vs E (incident photosynthetic active radiation) curve), ETR(max) (maximum relative ETR), E(k) (light saturation parameter) and F(v)/F(m) (maximum quantum efficiency of photosystem II of dark-adapted samples) were obtained using the Imaging-PAM. The level of discrepancy between conventional and Imaging-PAM systems was dependent on the type of sample, being more pronounced for MPB muddy sediments. This may be explained by differences in the depth integration of the fluorescence signal related to the thickness of the photosynthetic layer and in the light attenuation coefficients of downwelling irradiance. An additional relevant parameter is the taxonomic composition of the MPB, as cyanobacteria present in sandy sediments rendered different results with red and blue excitation light fluorometers. These findings emphasize the caution needed when interpreting chlorophyll fluorescence data of MPB communities.

INTERNAL HEMIPELVECTOMY: REPORT ONEIGHT CASES.

Internal hemipelvectomy is a surgical procedure adequate for treatment of certain tumors of the pelvic girdle. Being a lower limb-preserving approach, it is a therapeutic alternative to the classical interilioabdominal amputation and hip joint disarticulation. According to Enneking's classification, there are four types of internal hemipelvectomies, although the association of different types of resection in the same procedure is feasible if necesary. This surgical approach should be correctly indicated to positively affect the patient's morbidity, mortality and quality of life. We report eight cases of internal hemipelvectomy in patients diagnosed with tumors of the pelvic girdle. We also discuss the neoadjuvant and adjuvant treatments used, along with their follow-up.

Hemipelvectomia interna: relato de oito casos / Internal hemipelvectomy: report on eight cases

A hemipelvectomia interna é um procedimento cirúrgico adequado no tratamento de certos tumores de cintura pélvica. É uma alternativa terapêutica capaz de preservar o membro inferior do paciente, ao contrário das amputações clássicas como a amputação interilioabdominal (AIIA) e desarticulação coxofemoral. De acordo com a classificação de Enneking, existem quatro tipos de hemipelvectomia interna, mas, se for necessário, é possível a associação de diferentes tipos de ressecção em um único procedimento. É fundamental que esta cirurgia seja indicada de forma correta para que interfira positivamente na morbimortalidade e qualidade de vida do paciente. Relatamos oito casos de hemipelvectomia interna em pacientes diagnosticados com tumores de cintura pélvica, bem como os tipos de tratamento neoadjuvantes e adjuvantes a que eles foram submetidos e o follow-up dos mesmos.

Internal hemipelvectomy is a surgical procedure adequate for treatment of certain tumors of the pelvic girdle. Being a lower limb-preserving approach, it is a therapeutic alternative to the classical interilioabdominal amputation and hip joint disarticulation. According to Enneking`s classification, there are four types of internal hemipelvectomies, although the association of different types of resection in the same procedure is feasible if necesary. This surgical approach should be correctly indicated to positively affect the patient`s morbidity, mortality and quality of life. We report eight cases of internal hemipelvectomy in patients diagnosed with tumors of the pelvic girdle. We also discuss the neoadjuvant and adjuvant treatments used, along with their follow-up.

Tumor desmóide de parede torácica recidivado / Recurrent desmoid tumor of the chest wall

Tumor desmóide (TD) ou fibromatose agressiva é um tipo raro de neoplasia de partes moles que não causa metástases, mas apresenta alto poder de infiltração por estruturas músculo-aponeuróticas adjacentes. O tratamento é agressivo, consistindo principalmente em ressecção cirúrgica com margens livres, também contando com a radioterapia, utilização de antiinflamatório não esteroidal (AINE´s), agentes hormonais e quimioterapia. A incidência de recidiva local após tratamento primário é alta. O presente trabalho relata o caso de um paciente que apresentou tumor desmóide recidivado em dorso, sendo submetido à cirurgia, que consistiu em toracotomia, apofisectomia, osteotomia, biópsia de parênquima pulmonar de lobo inferior esquerdo, drenagem fechada de pleura, reconstrução imediata com rotação de retalhos musculares e colocação de tela. Após procedimento cirúrgico o paciente foi submetido a 23 ciclos de radioterapia associados a doses diárias de Tamoxifeno (40mg/dia). Trinta meses após cirurgia, o paciente encontra-se livre de doença, assintomático e em acompanhamento.

Desmoid tumor (DT) or aggressive fibromatosis is a rare type of soft tissue neoplastic disorder that does not metastasize, but is highly infiltrative on the adjacent muscle and aponeurosis. Treatment must be aggressive, and consists mainly of surgical resection with free margins, although radiotherapy, non-steroidal anti-inflammatory drugs, hormones and chemotherapy may be used. Local relapse rate after primary treatment is high. We report a patient who had a relapse of desmoid tumor on the dorsum, and who underwent thoracotomy, apophysectomy, osteotomy, biopsy of the left lower lobe of the lung, closed pleural space drainage, immediate reconstruction with rotation of muscle flaps and mesh repair. After surgery, the patient received 23 cycles of radiotherapy associated with tamoxifen (40 mg/day). Thirty months after surgery, the patient shows no signs of the disease, no symptons at all and is currently being observed.