Latitudinal gradients in macroalgal biodiversity in the Southwest Atlantic between 36 and 55°S

Different groups of marine benthic organisms show contrasting latitudinal patterns of biodiversity. The widely accepted paradigm of increasing biodiversity towards the tropics does not seem to be valid for macroalgal floras of the Southern Hemisphere. We compiled a database summarizing the distributional ranges of macroalgae along the coast of Argentina to test whether biodiversity decreases towards lower latitudes, as in the Pacific coast of South America, and whether breaking points in the geographical distribution can be recognized in one or more areas of the Southwest Atlantic south of 36°S. We found a clear trend of decreasing biodiversity with decreasing latitude. The interpretation of some biodiversity declines is confounded by changes in the intensity of the sampling effort. A 51% reduction in algal species richness between 42 and 41°S coincides with the boundary between the Argentine and Magellanic Zoogeographic Provinces. This sharp breaking point is related to a thermal anomaly caused by long residence times of water masses within San Matías Gulf, suggesting an upper thermal tolerance limit for most Antarctic/sub-Antarctic seaweeds. A further reduction occurs at 38–37°S. This breaking point can be explained by the disappearance of suitable hard substrata, since rocky outcrops give place to wide extensions of sandy beaches. The impoverished algal assemblage inhabiting the northern coast of Argentina is mainly related to the reduction or disappearance of the Antarctic/sub-Antarctic floristic component. This area is characterised by a predominance of widely distributed species, Chlorophytes and opportunistic filamentous or foliose algae.     

Planktic foraminifera from the southwestern Atlantic (30 °–60 °S): species-specific patterns in the upper 50 m

Planktic foraminifers were studied in 96 samples collected in the southwestern Atlantic (30 °–60 °S, along 53 °W) in November 1993, mainly from depths between 0 and 50 m. Very high proportions of juveniles (unidentified) were present throughout the area, especially north of 37 °S, where they accounted for up to 70–80% of all shells recorded. For most species no clear vertical specific stratification was detected in the 0–50 m layer. Zoogeographic grouping of the 18 species identified allowed the defining of 5 distinct zones along the transect: Subtropical (north of 31 °S, 80% warm water individuals); Warm-Transitional (34 °–37 °S, 35% warm water); Transitional (37 °–49 °S, 99% cold water); Subantarctic (49–55 °S, 100% cold water); and Antarctic (south of 56 °S, 100% cold water). Boundaries between foraminiferal assemblage zones are in good agreement with hydrological fronts described for the area. Comparison of the present data with planktic collections from the North Atlantic show large differences in the proportions of various taxa. In the 14–24 °C range, G. bulloides is much more abundant in the northern hemisphere than in the southern one, whereas G. quinqueloba G. inflata and G. rubescens show the opposite trend. On the other hand, temperature-related percentage contributions within the 14 °–24 °C range indicate that the preferred thermic régimes of the 9 species considered are remarkably similar in the North and South Atlantic collections compared. The southernmost planktic distributional ranges of selected warm water taxa are roughly coincident with those established previously on the basis of surface sediments, disagreements being chiefly attributable to selective dissolution on the bottom. In contrast, at the bottom percentages of cold water foraminifers (G. bulloides G. pachyderma) are significantly enhanced with respect to their planktic populations, and their sedimentary northward limits extend well beyond their maximum ranges in the upper-layer plankton. It is suggested that submergence of these cold water species and northward displacement at subsurface depths is chiefly responsible for the mismatching patterns observed. Dissimilar species proportions in both hemispheres and plankton-sediment uncoupling can conceivably engender erroneous conclusions when distributional data are used for paleoecologic reconstructions with the aid of numerical analyses such as the Imbrie-Kipp transfer-function technique.     

Environmental factors that define the spawning and nursery areas for Percophis brasiliensis (Teleostei: Percophididae) in a multispecific reproductive coastal zone, El Rincón (39°–41°S), Argentina

The spatial distribution of Percophis brasiliensis at different maturity stages and its relationship to environmental factors was evaluated in the El Rincon area (39°–41°S) between 1994 and 2008 during eight cruises carried out in spring. For this, a canonical correspondence analysis was used. Results indicate that bottom temperature and bottom salinity horizontal gradient (BSHG) were the most important variables affecting the spatial distribution of P. brasiliensis maturity stages. Juveniles were mainly located in shallow waters with low salinity, high temperatures and vertical stratification. Conversely, gravid and running individuals were found in high BSHG and low temperatures. This link suggests that adults spawn in a well-defined area of hydrographic conditions that would tend to retain pelagic eggs and larvae, thus minimizing dispersal, and ensuring their transport from the spawning to nursery areas. On the coastal shelf of El Rincon, the water mass circulation shows an anti-cyclonic gyre whose recirculation cell during spring and summer is more constrained to inshore areas than during winter. Maximum reproductive activity of P. brasiliensis coincides with the highest retention period; therefore, dispersal of early-life stages (eggs) depends on the circulation pattern and transport pathway which would contribute importantly to its recruitment variability.     

Eating catch of the day: the diet of porbeagle shark Lamna nasus (Bonnaterre 1788) based on stomach content analysis,and the interaction with trawl fisheries in the south-western Atlantic (52° S–56° S)

This work examined the diet of the porbeagle shark Lamna nasus in the south-west Atlantic Ocean (SWAO, Argentina, 52° S–56° S) by analysing the stomach content information obtained by scientific observers who sampled specimens captured as by-catch on-board commercial fishing vessels from 2010 to 2020. A total of 148 fishing sites were analysed, in which the estimated catch was composed mainly of hoki Macruronus magellanicus (56.00%) and southern blue whiting Micromesistius australis (33.13%). From 413 porbeagle sharks sampled (292 females and 121 males) ranging from 71 to 241 cm total length (L_T) (mean: 179.76 ± 26.74 cm), 310 (75.06%) contained food in the stomachs. The forage fish were mainly hoki M. magellanicus (23.53%) and southern blue whiting M. australis (19.05%), followed by the Patagonian sprat Sprattus fuegensis (4.48%) and nototheniids (1.4%). Cephalopods and crustaceans accounted for 10% of the diet. The estimated trophic level was 4.35. Generalized linear models revealed that the consumption of hoki M. magellanicus and southern blue whiting M. australis increased with the L_T of the porbeagle shark. Moreover, smaller porbeagle sharks preyed upon both small and large teleost fish, whereas larger porbeagle sharks predated exclusively upon large fish. The diet of porbeagle shark involved interactions with fisheries as it fed upon the fish species that constituted the main catch in the analysed fishing sites, as well as the main catches of the austral trawl fisheries. The ecological role of porbeagle shark observed in the SWAO exposed implications for fisheries management from a multispecies perspective.     

Reproductive biology of Rioraja agassizi from the coastal southwestern Atlantic ecosystem between northern Uruguay (34°S) and northern Argentina (42°S)

A total of 552 individuals of Rioraja agassizi (257 females and 295 males) were collected by bottom-trawl during research cruises. Sexual dimorphism was observed with females are heavier than males for a given total length (TL). Using logistic regression, it was determined that TL at 50% maturity of males was 475 mm TL and of females 520 mm TL. This estimation agrees with the morphological parameters measured. Although not statistically significant, a peak in reproductive activity was observed in males during late spring and summer. The monthly variation in the gonadosomatic index and oviducal gland width, together with the largest diameter of ovarian follicles, suggests that R. agassizi females have a partially defined annual reproductive cycle with two peaks, one from November (spring) to February (summer) and another in July (winter).     

Reinvestigation of conchostracans (Crustacea: Branchiopoda) from the Permian–Triassic transition in Southwest China

Sedimentary deposits of the Permian–Triassic transition are well-exposed in numerous outcrops of South China. Depending on the palaeogeographic positions of the sections, their lithofacies vary from fully marine, shallow marine, lagoonal, lacustrine, and fluvial to alluvial. In the present study, conchostracans (Crustacea: Branchiopoda) were newly collected from the continental deposits of the Kayitou and Jialingjiang formations around the Kangdian Highland elevated by the Emeishan Basalt in the southern Sichuan, western Guizhou, and northeastern Yunnan provinces. The conchostracan fauna of the Kayitou Formation is composed of Pseudestheria chatangensis, Euestheria fuyuanensis, and Euestheria sp. aff. E. gutta. These species occur in varying lithofacies types of different sections. In particular, the late Permian Pseudestheria chatangensis occurs in grey siltstones interbedded with pebbly sandstones, which are interpreted as lacustrine deposits. Euestheria fuyuanensis and Euestheria sp. aff. E. gutta were obtained from yellowish to greenish–grey clay- and siltstones, interpreted as coastal plain deposits. In comparison to other regions, occurrences of Euestheria gutta are indicative of an early Induan to Olenekian (Early Triassic) age. The fossil record of Euestheria fuyuanensis is so far restricted to a few occurrences in the Kayitou Formation of Southwest China and, therefore, using this species for long-distance biostratigraphic correlation requires further investigation. The distribution of late Permian pseudestheriid and Early Triassic euestheriid species in the respective sections possibly depends on the local lithofacies and, therefore, a diachronous age of the Kayitou Formation within the study area can be assumed. Additionally, Magniestheria sp. aff. M. mangaliensis and Magniestheria sp. aff. M. subcircularis were recorded in the Jialingjiang Formation, which represents a lithostratigraphic unit considered as late Early Triassic (Olenekian). Further investigations of both taxonomy and the real stratigraphic ranges of the conchostracan species as well as cross-correlations with other age data are recommended, in order to better constrain the position of the Permian–Triassic boundary and the specific timing of the terrestrial end-Permian mass extinction in continental deposits of Southwest China.     

Distribution of pelagic Ostracoda (Crustacea) inhabiting the waters around Svalbard (Arctic Ocean: 76°36–81°50N)

Although, pelagic Ostracoda are locally abundant component of the mesozooplankton in the waters around Svalbard, the group remains poorly characterised both taxonomically and ecologically. Herein, the spatial and vertical variations in abundances and species composition of the pelagic Ostracoda assemblages are examined and related to the water masses. The study is based on a series of zooplankton samples collected with a multinet plankton sampler (MPS; HydroBios, Kiel), consisting of five nets fitted with a 180-μm mesh net. Samples were collected from deep stations (i.e., with bottom depths >300 m) around Svalbard and included localities influenced by the West Spitsbergen Current and the East Spitsbergen Current and to the north of Svalbard, between years 2001 and 2006. Throughout all the samples studied Discoconchoecia elegans was the numerically dominant species. The other species found were Boroecia maxima, Boroecia borealis, Obtusoecia obtusata, and a rare novel Boroecia species. Analyses of the pelagic Ostracoda assemblages showed that their variability was predominantly influenced by four factors: water temperature, geographical position, bottom depth and season. The highest densities of D. elegans were correlated with salinities >35 PSU whereas B. maxima distribution was dependent on latitude. Highest concentrations of B. borealis were determined by longitude. Abundances of O. obtusata were positively correlated with warmer water temperatures. Thus this work suggests that halocyprids have the potential to be good indicators of environmental changes associated with shifts in climate at high latitudes in the North Atlantic.     

Fission–Fusion Dynamics in Southern Muriquis (Brachyteles arachnoides) in Continuous Brazilian Atlantic Forest

Fission–fusion social dynamics, the spatiotemporal variance in subunit size, composition, and cohesion, are the subject of considerable interest owing to their complex nature and widespread appearance in the primate order. We here aim to describe the nature of fission–fusion dynamics in a population of egalitarian southern muriquis inhabiting a relatively undisturbed extension of mildly seasonal Brazilian Atlantic forest to provide insights into the functions of fission–fusion dynamics and to examine the constraints on and opportunities for associations among individuals. We collected instantaneous scan samples and ad libitum data over a total of 13 mo in 2 yr (1599 observation hours) on subunit size at 2 spatiotemporal scales (party and nomadic party), party composition, spatial cohesion, and the behavioral context of fission–fusion events. These southern muriquis exhibited high levels of fission–fusion with significant variation in party size, cohesion, and composition. The group was weakly cohesive with a small mean party size (3.74 adults, 5.32 all individuals) and nomadic party size (13.73 adults, 19.38 all individuals). Mixed parties were the most frequently observed party type, although the high frequency of all-male parties suggests strong relationships based on philopatry and a mating strategy under scramble competition. We compare fission–fusion dynamics across populations of Brachyteles and highlight the striking continuum of these dynamics in the genus. We make interspecific comparisons with Ateles and Pan, with well documented high levels of fission–fusion, and demonstrate interspecific variation and convergence in grouping patterns.     

Spatio-temporal variability of ichthyoplankton and its relationship with oceanographic conditions at the shelf break off Chilean Patagonia (43°S–51°S)

Larval fish composition and abundance have been studied in fjords of south Patagonia. However, the ichthyoplankton of the adjacent shelf and slope waters of the Pacific Ocean, which is an important spawning and nursery ground for demersal fishery species (e.g. austral hake and Patagonian grenadier), remains largely unknown. To compare ichthyoplankton occurrence with environmental conditions in August 2013 and 2014 (austral winter), two bio-oceanographic cruises were carried out between 43° and 51°S. Conductivity, temperature and depth (CTD) data and ichthyoplankton samples were collected. The highest frequency of occurrence (FO) was observed for eggs of lightfish Maurolicus parvipinnis (84 and 91% FO in 2013 and 2014, respectively) and larvae of the myctophid Lampanyctodes hectoris (60 and 94% FO, respectively). Ichthyoplankton composition and abundance varied significantly between years, and richness varied from 10 (2013) to 18 taxa (2014). Only larval L. hectoris showed a significant increase in abundance during the winter of 2014. Water column temperature and salinity were significantly different between years; the water was warmer and saltier in 2013. Canonical Correspondence Analysis detected positive relationships between temperature and salinity with egg abundance and larval distribution of Merluccius australis. The highest abundance of eggs of M. australis was found at ～6–10°C, mainly off south Guafo Island. Additionally, ichthyoplankton from the shelf-break area off south Patagonia showed a wider latitudinal distribution in the winter of 2014 than in 2013.     

Phytoplankton distribution in the upwelling areas of the Moroccan Atlantic coast localized between 32°30'N and 24°N

Marine phytoplankton was studied in January and July 2002 along of four transects: 32°30′N, 29°N, 24°30′N and 24°N. A total of 142 taxa were recorded in this area. The maximal specific richness, both in summer and in winter, was registered around Dakhla (24°N). The global spatiotemporal variability of species richness and specific diversity showed that the most structured and species-rich populations are situated in the coastal areas. The vertical variation of the two parameters showed homogeneity between depth levels. The maximal phytoplanktonic densities are recorded in the southern transects due to the permanent upwelling activity in the southern Atlantic coast. The bathymetric distribution of densities was more heterogeneous during summer, characterized by a high intensity of upwelling. The species Thalassionema nitzschioides, Asterionellopsis glacialis, Melosira, Chaetoceros and Leptocylindrus minimus are indicators of upwelling.     

Exploring the clastogenic effects of air pollutants in S?o Paulo (Brazil) using the Tradescantia micronuclei assay.

This study was designed to determine the clastogenicity of particulate matter (aerodynamic diameter smaller than 10 microm) in the urban polluted air in the city of S?o Paulo. The Tradescantia-micronucleus (Trad-MCN) assay was used throughout this study to evaluate the clastogenicity of the extracts of the particulate matter. Tradescantia pallida (Rose) Hunt. cv. purpurea, an indigenous cultivar, was used in the Trad-MCN assay. The efficacy of this plant material for the Trad-MCN assay was validated with dose-response studies using formaldehyde and beta radiation. Dose-response curves were established with these known mutagens. The extracts of the PM10 particles at concentrations between 5 and 50 ppm induced a dose-related increase in MCN frequencies. The results indicate that T. pallida is equally sensitive to mutagens as the standard Tradescantia clone 4430 or 03 and the particulate matter in the urban air are clastogenic to the chromosomes of this plant. Inhalation of these particles by urban dwellers may affect their health by inducing similar genetic damage.     

Identification of the best ovitrap installation sites for gravid Aedes (Stegomyia) aegypti in residences in Mirassol, state of São Paulo, Brazil

This study aimed at identifying the best ovitrap installation sites for gravid Aedes aegypti in Mirassol, state of S?o Paulo, Brazil. Ovitraps were installed in ten houses per block over ten blocks. Four ovitraps were placed per residence, one in the bedroom, one in the living room, and two outdoors with one in a sheltered area and one in an outside site. Each week for eleven weeks, visits were made to examine the ovitraps and to change the paddles used for egg-laying. Eggs were analyzed according to the trap location. The results showed that the outdoor sites received significantly more oviposition than indoor sites. Additionally, in respect to the outdoor sites, the outside site received significantly more oviposition than the sheltered site. A strong correlation was observed between positive traps and egg numbers. The results are discussed with respect to the best installation site of the traps and their implications in surveillance and control of dengue vectors.     

Spatial-temporal variability of ultraplankton vertical distribution in the Antarctic frontal zones within 60–66°E, 43–46°S

The vertical distribution of heterotrophic bacteria and four ultraphytoplanktonic (<10 µm) groups (Prochlorococcus, Synechococcus, pico- and nanoeukaryotes) was investigated by flow cytometry at three process stations located in three different sub-systems belonging to the Antarctic Circumpolar Current frontal zone and to the Southern Indian Ocean (60–66°E, 43–46°S; ANTARES 4 cruise, January-February 1999): the Subtropical Zone (STZ), the Convergence Zone and the Polar Frontal Zone (PFZ). In each sub-system, short-term variability of cell abundance and flow cytometric parameters (right-angle light scatter and chlorophyll autofluorescence) was assessed through a times series of up to 24 h with a 2 h sampling frequency. The ultraphytoplankton vertical distribution exhibited a high spatial variability, with dominance of Prochlorococcus in the STZ (mean: 762.85×10¹⁰ cells m^–2), whereas picoeukaryotes (<3 µm) were dominant in the PFZ (55.46×10¹⁰ cells m^–2), a typically high-nutrient low-chlorophyll zone. Heterotrophic bacteria abundance was maximum (9.84×10¹³ cells m^–2) in the frontal zone, between the Agulhas Front and the Subtropical Front. Nanoeukaryotes showed the largest (up to 80%) variations between two consecutive sampling periods (2 h). Abundance variations could not be assigned to the same water mass during the time series due to the highly variable hydrodynamics of the study area. Trends of short-term abundance variations were opposite between the PFZ (lowest at night) and north of the Subtropical Front (highest at night). The observed spatial and short-term variations illustrate the complexity of the water masses in the Indian sector of the Southern Ocean, and highlight the challenge of extrapolating discrete measurements over space and time for use in evaluating carbon budgets in such dynamic areas.     

The long-term (1979–2005) effects of the North Atlantic Oscillation on wind-induced wave mixing in Loch Leven (Scotland)

We report on long-term covariation (1979–2005) between indices of the North Atlantic Oscillation (NAO) and wind speed and direction in Loch Leven. The effects of the observed variations in wind speed and direction were combined to produce modelled wave-mixed depths (Zc). Positive correlations were observed between seasonal and annual wind speeds and westerly frequency and indices of the NAO that are in line with general perception: positive NAO was correlated with stronger, more westerly winds and these correlations were strongest in winter and spring. Correlations between NAO and estimates of Zc were strongest in the most westerly exposed site in spring (r ² = 0.701; Zc_spring versus spring NAO index). On average, over a 25-year period Zc was deeper in spring and shallower in summer. Major anomalies from the 25-year seasonal means were observed in 1982, 1979, and 1991. Annual average Zc was low in the late 1970s and early 1980s (shallowest average annual Zc of 1.0 m (1984)), high in the late 1980s and early 1990s (deepest average annual Zc of 1.9 m (1990)) and moderate in recent years (up to 2005). This study has major implications for our understanding of potential climate change drivers and the related responses of shallow lake ecosystems, including alterations to littoral habitat quality and benthic–pelagic coupling.     

Diversity of phytoseiid mites (Acari: Mesostigmata: Phytoseiidae) in the Atlantic Forest of São Paulo

The objective of this study was to evaluate the diversity of Phytoseiidae in the Atlantic Forest of São Paulo State, Brazil, and to estimate the possible role of this ecosystem as a reservoir for mites of this family. Samples were taken from 187 plant species belonging to 73 plant families in three vegetation types of the Atlantic Forest, from February 2001 to October 2002. In total, 1102 specimens of 54 species belonging to 20 genera of the three phytoseiid subfamilies were found. Most specimens (93%) and species (91%) belonged to the Amblyseiinae. The majority of species found belong to taxonomic groups largely composed of generalist predators (especially Amblyseius and Euseius). In general, the more abundant mites were found on a diversity of plant species, but a few of the abundant species were found on only a small number of plant species. Only nine of the mites encountered during this study are of known agricultural importance. The results obtained suggest the importance of the wide plant diversity in the region to sustain a wide diversity of phytoseiids. The extensive clearance of the Brazilian Atlantic Forest is a threat to the diversity of these mites, important predators of mite pests.     

Using Local Ecological Knowledge to Assess Morel Decline in the U.S. Mid–Atlantic Region

Using Local Ecological Knowledge to Assess Morel Decline in the U.S. Mid–Atlantic Region. Morels (Morchella spp.) are prized wild edible mushrooms. In the United States, morels are the focus of family traditions, local festivals, mycological society forays, and social media, as well as substantial commercial trade. A majority of the anglophone research on morels has been conducted in Europe and in the U.S. Pacific Northwest and Midwest. This literature provides insights into a diverse and plastic genus, but much of its biology and ecology remains a mystery. In 2004, we initiated a study of morel mushroom harvesting in the U.S. Mid–Atlantic region in response to concerns that morels might be in decline in the national parks in that area. This paper presents results from that research with an emphasis on morel hunters’ local ecological knowledge of morel types, phenology, habitat, vegetative associations, and responses to disturbance. We conclude that experienced morel harvesters possess local ecological knowledge that complements scientific knowledge and can increase our understanding of the complex and regionally variable ecology of Morchella and inform conservation efforts.     

Changes in Habitat Suitability for the Tick Ixodes ricinus (Acari: Ixodidae) in Europe (1900–1999)

Climatic changes may lead to drastic changes in the distribution of arthropods important in human health. We tracked changes in habitat suitability for the tick Ixodes ricinus in Europe from 1900 to 1999, using a geographically extensive gridded climate data set. For the whole period, 52% of the territory was always unsuitable for the tick. In the grid, 6.11% of the cells were classified as having a deterministic drift with positive trend and 7.4% as deterministic drift with a negative trend. A total of 17.25% of cells were classified as exhibiting a random walk behavior, with a trend to increase of habitat suitability (9.57%) or decrease (7.68%). Zones of deterministic trend extend into most of Ireland and parts of the United Kingdom and France. Total and summer rainfall primarily drive changes in habitat suitability in these sites. Areas of random walk are common in Scandinavia, central Europe, and the Balkans, with summer rainfall and temperature largely directing the changes. Sites of reported increased abundance of I. ricinus coincided with areas of increased habitat suitability over the last 20–30 years, but this feature showed a long-term random walk negative trend. Habitat suitability for I. ricinus remains relatively stable in Europe, with no sites showing permanent changes in habitat suitability (negative to sustained positive or vice versa). However, some zones in the continent showed a clear trend to increase or decrease.     

Sedimentological and paleoecological aspects of the Norian–Rhaetian transition (Late Triassic) in the Xuanhan area of the Sichuan Basin,Southwest China

The end-Triassic mass extinction is one of the five big extinction events in the Phanerozoic, and its impact on marine organisms has been extensively studied. However, whether the terrestrial ecosystem had begun to deteriorate or even collapsed prior to the end-Triassic mass extinction remains controversial and the related studies in Asia are very limited. In this study, we provide a comprehensive investigation of the sedimentary environments, their implications for floral changes, and the paleoecology during the Norian–Rhaetian transition in Xuanhan area, northeastern Sichuan Basin, Southwest China. The sedimentary environments and climatic conditions changed coupling the transgression and regression caused by the tectonic movements. Climatic oscillations were identified during the Norian–Rhaetian transition in the Xuanhan area, including a short-term cooling event. The diversity and composition of the plant communities changed through the Norian–Rhaetian transition in Xuanhan area, but the terrestrial ecosystem as a whole didn’t collapse or deteriorate prior to the end-Triassic mass extinction.