Surf Diatom Research Articles

Surf-diatoms from sandy beaches on the Eastern Coast of South America (Brazil): the identification ofAnaulusEhrenberg andAsterionellopsisRound

Abstract“Surf diatoms” can form high biomass in the surf zone of sandy beaches around the world,AsterionellopsisandAnaulusbeing the main genera of this group in Brazil.Asterionellopsis glacialiswas considered a cosmopolitan species, and taxonomic studies using molecular and morphological tools showed thatA. glacialisis a complex with cryptic and semicryptic species. So, it would be plausible to suppose thatAnaulus australis, another surf zone patch-forming diatom with wide latitudinal occurrence could also be part of a species complex. We collected and identifiedAnaulusandAsterionellopsisstrains from tropical, subtropical and warm temperate sandy beaches on the east coast of South America (Brazil) based on genetic divergence, phylogeny, single-locus automated species delimitation methods (both genera), and frustule ultrastructure (Anaulus).AnaulusandAsterionellopsisshowed contrasting diversity patterns and spatial distribution: a single species ofAnaulus australiswas registered in tropical and subtropical beaches, while at least three species ofAsterionellopsis:A. tropicalis,A. thurstoniiandA. guyunusaewere observed at different latitudes, indicating thatAsterionellopsisspecies have distinct ecological requirements.Asterionellopsis thurstoniiwas previously reported in Europe and it is documented here for the first time in the Southern Hemisphere. The different diversity patterns between these two surf diatom genera suggest that they are likely to have distinct ages, and dispersion and/or speciation processes.

Association of early stage fishes with surf diatom Anaulus australis accumulations in a warm temperate surf zone, South Africa

Surf zones are recognised as important nursery habitats for early stage fishes worldwide, but microhabitat opportunities for feeding and refuge are not well studied. Surf diatoms accumulate in high densities, discolouring the water and offering potential refuge and feeding opportunities. The aim of this study was to investigate the association of early stage fishes with surf diatom Anaulus australis accumulations in the Sundays Beach surf zone on the South African southeast coast. Early stage fishes were sampled within and outside of visible A. australis accumulations using a 4.5 × 1.5 m larval fish seine net with 500 μm mesh. Over 22 sampling trips, 338 replicate samples were collected. Species diversity, the overall catch per unit effort (CPUE) and that of the dominant species Chelon richardsonii, Diplodus capensis, Rhabdosargus globiceps and R. holubi, were significantly higher within accumulations compared to outside. Postflexion larvae and early juveniles occurred in significantly higher numbers within accumulations, indicating that fishes were actively selecting A. australis accumulations. Generalized linear models revealed that temperature, dissolved oxygen (mg l−1), turbidity and A. australis biomass (μg Chl a l−1) were the most significant variables correlated with the overall CPUE and that of dominant species. Since A. australis accumulations have a patchy distribution in the surf zone, it is suggested that early stage fishes are opportunistically using this resource when and where it occurs as both a feeding and refuge area. Understanding the role of microhabitats for early stage fishes is essential for understanding survival and life history strategies within the mosaic of coastal nursery areas.

Feeding ecology and microplastic ingestion in Chelon richardsonii (Mugilidae) associated with surf diatom Anaulus australis accumulations in a warm temperate South African surf zone

The study aimed to explore ontogenetic dietary changes and microplastic ingestion in Chelon richardsonii associated with diatom Anaulus australis accumulations in a warm temperate South African surf zone. This species is commercially important and forms an important trophic link in southern African coastal waters. Postflexion larvae, juveniles and adults are dominant in surf zones and were used for comparison. Index of Relative Importance (%IRI) results showed an ontogenetic dietary shift, with postflexion larvae ingesting mostly copepods (%IRI = 52.0) and microplastic fibres (%IRI = 30.7); while older developmental stages fed predominantly on diatoms (%IRI ranging from 53.9 to 65.6) and sand (%IRI ranging from 34.2 to 46.0). Microplastic fibres were found in 40% of fish sampled, microplastic fragments in 5%, and both types were recorded across all developmental stages assessed. This study provides the first record of microplastics in C. richardsonii, adding to growing microplastic research in fishes.

Attheya armata along the European Atlantic coast – The turn of the screw on the causes of “surf diatom”

The “surf diatom” species Attheya armata (West) Crawford accumulations have been detected in the coasts of Galicia (NW Spain) in recent years. However, unlike in other parts of the world, the current knowledge of the phenomenon in European coasts remains disperse and scarce. A multiple approach has been used to monitor a sector of the Galician coast and to evaluate chemical and biological parameters in the environment, as well as under in vitro culture conditions, with the aim of studying the causes underlying these episodes. Contrary to the general assumption, our results indicate no direct relationship between the ephemeral accumulation episodes occurrences with the continental discharges or nutrient levels in beach waters. The isotopic reference values for coastal food web in Galicia allows to affirm with certainty that A. armata accumulations is dominate by the sediment dynamics.

Ecophysiological and biochemical variation of the surf zone diatom asterionellopsis glacialis sensu lato from Santa Catarina, Southern Brazil

Abstract Patches formed by dense accumulations of diatoms in the surf zone (surf diatoms) are common on sandy beaches with intermediate to dissipative morphodynamic states. Their appearances are correlated with environmental factors such as the passage of cold fronts when onshore winds increase beach hydrodynamics, resuspending epibenthic stocks and accumulating them through the inner surf zone. In Santa Catarina state, Southern Brazil, two beaches are known to have frequent occurrence of accumulations of the surf diatom Asterionellopsis glacialis sensu lato: Rincão Beach (28°50' S) and Navegantes Beach (26°52' S). The high biomass of this alga and its central importance in the trophic structure of the coastal ecosystems suggest studies about its potential applications. In the present study, strains of A. glacialis were isolated, cultured under different conditions and evaluated for ecophysiological aspects: growth rate under different conditions, potential biological activities of exudates, biomass and lipid content, and fatty acid profile. A. glacialis cells in culture showed deformation, which were ameliorated by using agitation and silicon and phosphorus enriched culture media. Exudates of the strains showed no allelopathic effects, although previous studies have indicated activity. Lipid content showed variation depending on the strain and culture media. Values ranged from 9% to 13.6% by dry weight. In all strains saturated fatty acids and polyunsaturated fatty acids were identified. Some hypotheses were proposed to explain the variation of the lipid contents, fatty acid profiles and physiological features between strains of the same species. We believe that the fatty acids profile of this primary producer has important consequences in the sandy beach ecology.

Assessment of surf zone environmental variables in a southwestern Atlantic sandy beach (Monte Hermoso, Argentina)

The aim of this study was to investigate the temporal dynamics (monthly/tidal) of water temperature, salinity, chlorophyll-a (chlo-a), suspended particulate matter (SPM), particulate organic carbon (POC), and dissolved nutrients in the surf zone of Monte Hermoso sandy beach, Argentina. We also aimed to understand the underlying mechanisms responsible for the observed variability. Sampling was carried out approximately monthly (September 2009-November 2010), and all samples were collected in a fixed station during high and low tide. Water temperature showed a clear seasonal variability (July: 9°C-December: 26.5°C) and a thermal amplitude of 17.5°C. Salinity ranged from 33 to 37, without a pronounced seasonality. SPM (10-223mgL(-1)) and POC concentrations (399-6445mg Cm(-3)) were high in surf zone waters. Chlo-a (0.05-9.16μgL(-1)) was low and did not evidence the occurrence of surf diatom accumulations. Dissolved nutrient concentration was quite fluctuating. None of the variables seemed to be affected by tidal stage. The results showed how fluctuating the physico-chemical and biological variables can be in this particular system. The observed variability can be related with local beach conditions but also with regional processes. The study area is highly influenced by a neighbor estuary and as a consequence, could be vulnerable to their seasonal and inter-annual dynamics. All of these characteristics must be considered for further studies and planning of the uses of natural resources and should be taken into account in any environmental monitoring program conducted in a similar beach system.

Pulse of marine subsidies: the role of surf diatom Asterionellopsis glacialis accumulations in structuring the meiofauna of sandy beaches

Resource subsidies are flows of biologically fixed energy and nutrients from one ecosystem to another. Oceanic sandy beaches are typical examples of systems constantly subjected to subsidies. A distinctive feature of some exposed sandy beaches is the brown discoloration of surf zone waters due to rich accumulations of diatoms housed on the sediments seaward of the breaker zone. Large amounts of the rich diatom accumulations may end up on the sediments of surf and the intertidal zones of sandy beaches. In this study, we described the seasonal frequency and compared the strength the subsidies among different beaches by measuring sediment chlorophyll a and total organic content. We hypothesized that large amount of fresh diatom subsidies to beaches sediment will fuel meiofauna from the surf zone to the upper intertidal and change the structure of these communities. Our results supported that pulsed subsidies by the deposition of A. glacialis represented an important resource for the meiofauna. The meiofauna responded quickly to the increase in concentrations of labile organic matter in the sediments along different tidal levels of the beach. This subsidized input, however, is not an isolated process but linked with the passage of cold fronts and significant physical changes in the surf zone. Subsides did not fuel surf and intertidal meiofauna similarly. At the surf zone, subsidies were mainly used by those forms that cope with increasingly turbulent flows that paralleled the accumulation events. Yet in the intertidal zone, the densities and richness of the most abundant meiofauna organisms, the nematodes, thrived together with other meiofaunal organisms. Due to their frequency over the time and differences on space, A. glacialis patch deposits most certainly are not the main food item for high-energy sandy beach consumers, but accumulations do represent a window of opportunity for meiofauna during the year, particularly in periods of food shortage during winter.

Surf zone diatoms: A review of the drivers, patterns and role in sandy beaches food chains

The accumulation of high biomass of diatoms in the surf zone is a characteristic feature of some sandy beaches where the wave energy is sufficiently high. A few species of diatoms, called surf diatoms, thrive in this harsh environment. The main processes driving the spatial and temporal distribution of surf diatoms as well as their standing biomass and growth were described twenty to thirty years ago based on studies conducted on the western coast of the United States of America and South African beaches. Since then, over fifty locations around the world have been reported to have surf diatom accumulations with most (three-quarters) of these being in the southern hemisphere. Their occurrence is controlled by physical and chemical factors, including wave energy, beach slope and length, water circulation patterns in the surf zone and the availability of nutrients to sustain the high biomass. The main forces driving the patterns of temporal variability of surf diatom accumulations are meteorological. In the short term (hours), the action of wind stress and wave energy controls the diatom accumulation. In the intermediate time scale (weeks to months), seasonal onshore winds of sufficient strength, as well as storm events are important. Furthermore, anthropogenic disturbances that influence the beach ecosystem as well as large-scale events, such as the El Niño Southern Oscillation, may lead to significant changes in surf diatom populations in the long term (inter-annual). Surf diatoms form the base of a short and very productive food chain in the inshore of the sandy beaches where they occur. However, the role of surf diatoms in the microbial food web is not clear and deserves further studies.

A low-latitude bloom of the surf-zone diatom, Anaulus australis (Centrales, Bacillariophyta) on the coast of Southern Queensland (Australia)

A novel bloom of the surf diatom Anaulus australis Drebes et Schultz was observed in subtropical waters off Surfers' Paradise, Queensland, Australia (27 degrees 55'S; 153 degrees 23'E) in early May 2000. This is the lowest latitude in which an Anaulus australis surf diatom bloom has been reported. Nitrogen stable isotope analysis of surf diatoms may indicate anthropogenic nutrient inputs in this environment.

Growth rates of five species of subtidal clam on a beach in the South Island, New Zealand

Growth rates of five species of New Zealand surf clams were estimated at Cloudy Bay, Marlborough, from analyses of sequential length-frequency samples with the computer program MULTIFAN and analyses of incremental growth of marked individuals with the computer program GROTAG. The von Bertalanffy parameters k and L∞ estimated by MULTIFAN were: Paphies donacina, 0.33 and 94.1; Spisula aequilatera, 1.01 and 60.3; Mactra murchisoni, 0.57 and 88; M. discors, 0.41 and 68; data for Dosinia anus could not be analysed reliably. These parameters estimated by GROTAG were: P. donacina, 0.35 and 84.8; S. aequilatera, 1.74 and 57.6; M. murchisoni, 0.58 and 80.6; M. discors, 0.54 and 61.5; D. anus, 0.36 and 61.6. The age-based growth estimated by MULTIFAN is not strictly comparable with the length-based growth estimated by GROTAG, but graphical comparisons show that both programs estimate similar growth rates for each species of surf clam. Interspecies differences in growth rates are hypothesized to be related to differences in species depth distribution within the surf zone. S. aequilatera, with the highest growth rate, is found just inshore of the primary wave break, where surf diatom abundance is postulated to be highest. An extension to the linear growth model of GROTAG that allows the predicted growth of larger animals to decline asymptotically to zero and never be negative is presented.

Dark Survival of the Surf Diatom Anaulus australis Drebes et Schulz

The surf diatom, Anaulus australis Drebes et Schulz, requires a mechanism to survive the prolonged dark conditions to which it is periodically exposed during calm conditions. This study examined various aspects of A. australis cells kept in the dark for a prolonged period. While many cells became distorted or damaged and were obviously no longer viable, the cytoplasm of some cells became dark and compact suggestive of a resting phase. The physiological activity (photosynthesis and respiration) of the population was reduced to zero within 20 days of darkness. After cells were kept in the dark for more than 2 months, some rapidly regained their full physiological potential (...)

The relative quantities of live and detrital organic matter in a beach-surf ecosystem

Detrital standing mass measured along the Sundays River Beach, South Africa, was consistently high within the surf-zone, exceeding values recorded in the immediate offshore by a factor of 4. An average detrital load of 3.5 kg C per running meter of beach (· m −1) was estimated for the beach-surf ecosystem, making up 91% of the total POC. This component would appear to represent a major C source to the food chains of the ecosystem, contrary to the current concept where the ecosystem is considered to be fuelled primarily by the conspicuous surf-diatom population. A different situation exists within the inner surf-zone, where nearly 50% of the POC is living material consisting of high concentrations of the surf diatom Anaulus birostratus (Grunow) Grunow. This 1:1 ratio is restricted to daylight hours when dense phytoplankton patches are present within the inner surf-zone. At night when the surf-diatom cells become epipsammic, the ratio shifts in favour of detritus. The trophic significance of these POC components is not commensurate with their respective contribution to the POC pool, since A. birostratus cells are of an enhanced value to consumers because they accumulate into patches, reaching concentrations of 10 9 cells · 1 −1. A sharp decrease in the shore-normal distribution of detritus and inorganic matter in the water column occurs at the junction between the rip-head zone and the nearshore. The sudden changes provide further evidence that the seaward limit of rip-heads is the outer boundary of beach-surf ecosystems.

The use of false buoyancies by the surf diatom Anaulus birostratus in the formation and decay of cell patches

We describe a shift in our understanding of cell patch dynamics in the surf diatom Anaulus birostratus (Grunow) Grunow as a result of recent findings concerning their vertical distribution. An extension of previous investigations to include the psammic or sediment habitat of the surfzone has shown this surf diatom to alternate from a planktonic and neustonic life mode during the day to epipsammic at night. The pattern and magnitude of this shift are discussed in the light of existing hypotheses, and form the basis of a new approach to the question of patch formation and decay by surf diatoms. Briefly, cells acquire a positive buoyancy during the day, enabling them to occupy the air/water interface despite their high specific gravity. This positioning allows for the build-up of a concentration gradient in the inner surfzone in spite of the excessive offshore drainage brought about by rip activity. The resultant concentration of cells at the surface is a major causal factor involved in patch formation. Evidence is provided to show that during the late afternoon cells switch adherence from air bubbles to sediment particles in order to enter the sediment. In this way the patch disappears but the cells are retained within the inner surfzone. The cycle is repeated when the epipsammic cells elute out of the sand in the early morning. In the absence of cell patches there is still a resident sediment population, although cell numbers are two orders of magnitude lower. We also observed that under these circumstances the elution process in the early morning was suppressed. Preliminary data obtained for other surf diatoms at the Sundays River Beach, South Africa, suggest the dynamics described above for A. birostratus to be common to this group of marine phytoplankton.

Distribution patterns of the surf diatom Anaulus birostratus in an exposed surfzone

We report on the spatio-temporal distribution of Anaulus birostratus (Grunow) Grunow within a beach/surfzone ecosystem as observed during five case studies. The first three exercises consisted of a time-series of observations where the coastal zone was stratified into sub-environments and sampled concurrently. The results indicate definite instances of major temporal changes in the position and structure of the surf diatom population. On certain occasions these changes were accounted for by onshore/offshore shifts in the population, i.e. decreases in the surfzone population size being accounted for by simultaneous increases in the nearshore population and vice versa. In contrast to the above, the entire population was occasionally restricted to the surfzone. The source of incoming cells responsible for the early morning increases in cell concentration could not be established, nor was it possible to trace the exodus of cells in the late afternoon when cell patches disappeared. It is proposed, therefore, that the dynamics of surf diatom populations are more complex than had been anticipated, involving more than one mode of cell advection. The remaining two case studies provided conclusive evidence on the general impermeability of the breaker line to surfzone A. birostratus cells during the day time. This filter action is proposed as the mechanism for patch formation because it allows for the build-up of a concentration gradient in the inner surfzone. A. birostratus cells were restricted to the surfzone and rip-head region. Within this area cell division was restricted largely to the inner surfzone and the nearshore fraction is therefore expected to represent a dormant population.

The Response of Surf Diatom Populations to Environmental Conditions. Changes in the Extent of the Planktonic Fraction and Surface. Patch Activity

Article The Response of Surf Diatom Populations to Environmental Conditions. Changes in the Extent of the Planktonic Fraction and Surface. Patch Activity was published on January 1, 1988 in the journal Botanica Marina (volume 31, issue 2).

Rip current charactersitics and their role in the exchange of water and surf diatoms between the surf zone and nearshore

Photogrammetric measurements of dye dispersion in a high-energy surf zone provided semi-quantitative measurements of the pattern and flux of water exchange between the surf zone and nearshore. The intensity of current flow, the rip morphology and its position within the surf zone have important ecological implications for the surf zone and nearshore biota. A variety of water-movement patterns was found, ranging from currents which remained confined to the beach terrace to those which involved substantial exchange across the breaker line. In considering rips as exchange mechanisms, two rip types are recognized. Depending on the exchange of water across the breaker line, a rip may be classified as ‘exchange’ or ‘non-exchange’. The ecological significance of these current types is discussed and a classification scheme for rip currents is proposed. Offshore fluxes across the breaker line by rip currents ranged from negligible to 80 m 3s −1 rip −1. The estimated maximum flux per running meter of the Sundays River Beach was calculated as 0·0.32m 3 s −1. The half-residence period of surf-zone water ranged from as little as 22 min t0 5 days, averaging 3·6 h. A dichotomy of current patterns found between the water column and surface layers is used to explain the build up of a concentration gradient in cell numbers of the surf diatom Anaulus birostratus within the surf zone despite extensive flushing by surf circulation.

The Spatial Dynamics of Surf Diatom Patches in a Medium Energy, Cuspate Beach

The Spatial Dynamics of Surf Diatom Patches in a Medium Energy, Cuspate Beach

Mullet grazing on surf diatom accumulations

Grazing by southern mullet, Liza richardsoni (Smith), on surf diatoms occurring in bloom concentrations off an ocean‐exposed East Cape beach, South Africa, was investigated. Field observations and stomach content analysis demonstrated that surf diatoms taken from the air‐water interface were a principal source of food. A qualitative examination of stomach contents revealed a feeding transition from planktonic carnivore in juveniles to a diet consisting entirely of surf diatoms in larger fishes. This change in diet commonly occurred at a standard length of 50–135 mm. Fish larger than 135 mm fed entirely on surf diatoms which were ingested together with large quantities of beach sediment. Grazing on surf diatoms only took place during daylight hours. Energy, ash, protein, fat and carbohydrate content determinations indicate a high food quality of surf diatoms. It is concluded that surf diatom accumulations form a richly concentrated and reliable food source of high nutritional quality for these fish. Possible widespread grazing on surf diatoms by mullets is considered.

Persistent blooms of surf diatoms (Bacillariophyceae) along the Pacific coast, USA. III. Relationships between diatom populations and environmental variables along Oregon and Washington beaches (1977 and 1978)

The surf diatom populations and environmental conditions at 13 beaches along the Oregon and Washington coasts were studied from June 1977 through August 1978. Spearman rank correlation coefficients were calculated for 14 environmental variables and seven species. Cell numbers of four of the species (Chaeloceros armalum, ASlerionella socialis, Biddulphia aurita, and Aulacodiscus kittonil) were positively correlated with rainfall and river discharge and negatively correlated with air temperature, water temperature, salinity, upwelling, daylength, and nitrogen (nitrate and ammonium) concentrations. These four species are stable members of the surf ecosystem. The remaining three species (Thalassiosira pacifica, Skeletonema costatum, and Asterionella glacialis) exhibited weaker correlations that were consistently opposite in direction to the correlation coefficients calculated for the surf diatoms, above.

Persistent blooms of surf diatoms along the pacific coast, U.S.A.: I. Physical characteristics of the coastal region in relation to the distribution and abundance of the species

The surf diatom populations at thirteen beaches along the Oregon and Washington coast were studied from June 1977 through August 1978. Chaetoceros armatum T. West and Asterionella socialis Lewin & Norris, the two species responsible for the blooms, were present in the surf along beaches between Point Grenville, Washington, and Cape Blanco, Oregon. On the basis of the cell densities of these two species, the beaches were arranged into four distinct groups. Discriminant analysis showed that the four groups could also be completely separated by three discriminant functions composed of four physical variables: offshore bottom slope, per cent chlorite, per cent montmorillonite and beach length. The absence of surf diatoms at two beaches south of Cape Blanco can probably be explained by the unsuitable physical conditions along the coast south of the Cape.