Effect of environmental factors on the spatial distribution of the epifauna of the alga Halopteris scoparia in Algeciras Bay, Southern Spain

The physical characteristics and environmental versatility of the alga Halopteris scoparia (Phaeophyta, Sphacelariales) make it a suitable substrate for development of epiphytic communities. Spatial variation of the epifauna on this alga in Algeciras Bay (southern Spain) in response to different environmental conditions is investigated. There is a clear difference in community composition between external and internal areas of the bay, with an important group of species present in only one of the areas (e.g., in outer areas crustaceans such as Tanais dulongii or Amphilochus neapolitanus or the polychaete Nicolea venustula; and species from inner areas such as the crustacean Jassa marmorata and the mollusc Alvania montagui or Rissoa similis). The external zone shows high hydrodynamics and low sedimentation rates, whereas in the internal one, there is a high sedimentation rate (as a result of two main rivers, a less strong current regime, and the presence of urban and industrial wastes). The conditions prevailing in the internal zone of the bay are unfavourable for most of the epifaunal species in the external bay areas.     

Ultrastruttura della cellula apicale di Halopteris scoparia (L.) Sauvageau (Phaeophyceae,Sphacelariales)

Abstract

Ultrastructure of the apical cell of Halopteris scoparia (L.) Sauvageau (Phaeophyceae, Sphacelariales). - The ultrastructure of resting apical cells of Halopteris scoparia (L.) Sauvageau from material collected in December is described. The cytoplasm is higly vacuolated with lipids, poliphenolic substances and polisaccharides occurring inside the vacuoles (the classic « physodes »).

Two cell organelles are prominently active at this stage: conspicuosly hypertrophic dictyosomes and the budding endoplasmic reticulum. Both light and electron microscope observations show that the cell wall has an outer stratification and inner discontinuous thickenings, the constituent material of which is uniformerly dispersed.

The above observations point out that the apical cell of Halopteris scoparia at this stage of its life cycle is engaged in an elaboration of vacuolar and parietal substances which will be therefore readly available at the outset of the growing season.     

DISTRIBUTION OF MOLLUSCS ACROSS A PNEUMATOPHORE BOUNDARY IN A SMALL BAY IN NORTHWESTERN AUSTRALIA

The number of species, total density and total biomass of molluscswere examined for 50 m either side of an Avicennia pneumatophoreboundary in the Bay of Rest, North West Cape, Western Australia(22°18'S; 114° 08'E). Two mollusc assemblages were found,separated almost exactly at the pneumatophore boundary. Themudflat association had more species of molluscs but a lowertotal density and total biomass than the assemblage in the Avicenniazone. Stations among pneumatophores on the seaward fringe ofthe Avicennia zone were more diverse and had a greater densityand biomass than stations among the trees. Possible reasonsfor the pneumatophore area having a higher density and biomassof molluscs than the adjacent mudflat and tree zones are discussed. (Received 18 June 1985;     

Topographically generated fronts, very nearshore oceanography and the distribution and settlement of mussel larvae and barnacle cyprids

Flow patterns adjacent to shore may prevent or aid shorewardmigration of benthic invertebrate larvae. We hypothesized thata front at the mouth of Sunset Bay, Oregon, prevents shorewarddispersal of larvae, significantly altering settlement of mussellarvae and barnacle cyprids. Settlement was measured at threesets of moorings (three moorings per site) distributed acrossthe front at Sunset Bay. From 6 July to 4 September 2000, sampleswere collected roughly every other day. Concurrently, we madevertical zooplankton tows adjacent to each mooring site andcollected physical oceanographic data. During upwelling-favorablewinds, the front was always present at the bay mouth, separatingsignificantly cooler, saltier and denser offshore water fromthat within the bay. During downwelling winds, the front brokedown and we found no significant difference in the surface physicaloceanographic parameters across the bay mouth. During upwelling,the concentration of mussel larvae was higher seaward of thefront than landward, but there was no significant differencein concentration during downwelling, suggesting that the frontmay act as a barrier to the shoreward dispersal of mussels.Mussel settlement was too low and sporadic to allow statisticalanalysis. There was no difference in cyprid concentrations acrossthe bay mouth whether the front was present or not. Cyprid settlementwas, however, nearly an order of magnitude lower at mooringsseaward of the front than at those landward. A significant cross-correlationwas found between settlement at the offshore mooring and tidalrange (r = 0.464, lag = 0 days) and between settlement at themid and inner moorings and downwelling winds (r = 0.532 midbay, r = 0.532 inner bay, lag = 0 days). Seaward of the front,settlement varied with tidal range, while landward of the front,most settlement occurred as brief pulses during downwellingwinds, periods when the front was not present. We found largedifferences in the distribution of cyprids, and mussel larvaeand cyprid settlement relative to the front; larval distributionsand settlement varied with upwelling versus downwelling windsand was due to differences in the very nearshore (i.e. within100–1000 m of shore) coastal oceanography.     

AN HOLISTIC APPROACH TO THE MANAGEMENT OF WATER QUALITY IN FALSE BAY,CAPE TOWN,SOUTH AFRICA

Summary

An overview of the water quality status of False Bay identified the bacterial/viral water quality of stormwater and rivers discharging near contact recreation beaches to be the management concern of highest priority. A second water quality concern is the potential impact of nutrients being discharged into False Bay on the surf zone and bay ecosystems. Heavy metals, hydrocarbons and industrial chemical discharges into the Bay are not regarded as a serious water quality threat. Much of the future development planned for Metropolitan Cape Town will impact on the volume and water quality of rivers, groundwater, stormwater and wastewater flowing into False Bay; hence the need for an integrated catchment management approach to the management of the bay.

An assessment of the constraints facing the holistic management of the bay and catchment concludes that the four main concerns are: (1) a lack of key research information on the options for stormwater management, and on the loading and potential impacts of nutrients being discharged into the surf zone and bay ecosystems; (2) jurisdictional fragmentation, and the lack of coordinated policy and planning between different local and government authorities and other users; (3) legislative fragmentation; and (4) a lack of private sector and public consultation by authorities. Preliminary ideas on the structure of a management body for False Bay and its catchment which address the concerns listed above are presented.     

2. NOTES ON THE STATUS OF SOME PALAEARC-TIC MIGRANTS IN NORTHERN RHODESIA

Whitfield, A. K. &; Cyrus, D. P. 1978. Feeding succession and zonation of aquatic birds at False Bay, Lake St Lucia. Ostrich 49:8-15.

Seasonal fluctuations in water levels at Lake St Lucia resulted in the inundation of depressions adjacent to the lake. Backwaters formed and were immediately colonized by aquatic invertebrates and fishes. Piscivorous birds dominated the early stages of the backwater feeding aggregations but with the decrease in water levels due to evaporation, crustacean and mollusc feeding birds became abundant. Both piscivorous and invertebrate-feeding wading birds formed a series of overlapping zones parallel to the shoreline.     

EFFECT OF DIFFERENT MOLLUSC ASSOCIATIONS ON TARGET MOLLUSC GROWTH AND PARASITE CERCARIAL PRODUCTION IN THE TRIPLE SYSTEM: BULINUS WRIGHTI-SCHISTOSOMA BOVIS AND MELANOPSIS PRAEMORSA

The influence of different mollusc associations in the triplesystem: Bulinus wrighti (target mollusc: TM)—Schistosomabovis (parasite)—Melanopsis praemorsa (non-target mollusc:NTM) is analysed. The results show that: (i) for a TM/NTM densityratio of 1/1, the NTM stimulates both growth of the TM and parasitecercarial production; (ii) for a TM/NTM density ratio of 1/5,the effects of the NTM on TM growth and cercarial productionwere not additive and were less marked than for the 1/1 ratio.Hypotheses on a chemical explanation for these density-dependenteffects are discussed. (Received 30 December 1991; accepted 9 March 1992)     

INVESTIGATION OF THE ACIDIC ALLOMONE OF THE GASTROPOD MOLLUSC PHILINE APERTA BY MEANS OF ION CHROMATOGRAPHY AND HISTOCHEMICAL LOCALISATION OF SULPHATE AND CHLORIDE IONS

Improved methods of collection of acidic allomones from theskin of the gastropod mollusc Philine aperta minimised contaminationby the anions of sea water and of blood. Neat allomone extractsremained stable in the laboratory for up to 15 months at 5–8°C,having a pH value of 2–3. Diluted extracts (1: 9 or 1:99) gradually lost their activity. Analyses by the Dionex H.P.ion chromatography apparatus showed that organic ions were presentonly in trace quantities in the allomone samples, and the principalinorganic anions were chloride and sulphate (their concentrationsapproached parity in the purest preparations). Measurementsof Cl^– varied in different samples from 2062 to 3989 p.p.million, and of SO₄^2–from 1272 to 3152 p.p. million. TheSO₄^2- CI^- ratios varied from 0.62 to 0.84. New observations are presented on the rate of in situ precipitationof BaSO₄ in preparations of the skin of Philine. The rate ofpenetration of BaCl₂ into the skin was approximately linear,even when the animal had become moribund (30 min). BaSO₄ crystalgrowth increased during the first 30 min of exposure, but laterdeclined, for reasons that are not clear. The method yieldedclear outlines of the acid sacs in histological preparations. A silver nitrate irrigation method was devised in order to investigatechloride ions in the acidic epithelium of Philine. The advanceof AgNO₃ into the tissue was usually smooth-fronted, but siteswere evident where the acid sacs had acted as channels for penetration.The silver deposits took the form of uniform small particles,often precipitated against the inner wall of an acid sac, butsometimes forming a central cluster. The method was of valuein building up a picture of structural relations as well asthe chemical composition of the acid sacs of Philine (Received 18 February 1985;     

Current distribution and potential expansion of the harmful benthic dinoflagellate Ostreopsis cf. siamensis towards the warming waters of the Bay of Biscay,North-East Atlantic

In a future scenario of increasing temperatures in North-Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellate Ostreopsis cf. siamensis has to be evaluated and monitored. Microscopy observations and spatio-temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south-east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time-series collected on plastic samplers showed that the species occurs in the bay from April to September. Due to the water circulation, colonization of the whole bay from the southern blooming zones is explained by inter-site connectivity. Key areas in the middle of the bay permit continuous dispersal connectivity towards the north. These key areas are proposed as sentinel zones to monitor O. cf. siamensis invasions towards the presumably warming water of the North-East Atlantic.     

HUMAN ACTIVITIES AND FACTORS AFFECTING THE DISTRIBUTION OF MACROBENTHIC FAUNA IN SALDANHA BAY

Summary

The most recent trends in the economic development of Saldanha Bay are towards the tourist and mariculture industries, both of which are dependent on a high quality of water. Yet this water quality is now under threat. In this study, the extent of human induced changes to the characteristics of the water body are assessed in terms of their effects on the macrobenthic communities of the bay. Such effects are evaluated on the basis of changes in biomass, community structure and species composition using data from recent surveys as well as a limited quantity of historical data.

Whilst gross effects are essentially confined to an area adjacent to the major fish factory outfall, the data do suggest a broader impact. There are substantial differences between the communities of ‘Big Bay’ and ‘Small Bay’, with an apparent increase in deposit feeding species and decline in suspension feeders in the latter. These changes are attributed to the organic loading from the fish factories and mariculture industries together with restrictions imposed on water circulation by harbour constructions. This combination of anthropogenic factors may be leading to significant enrichment of certain areas of the bay.     

Contributions of benthic and planktonic primary producers to nitrate and ammonium uptake fluxes in a nutrient-poor shallow coastal area (Corsica, NW Mediterranean)

By using the stable isotope ¹⁵N, we have measured in situ the uptake of nitrate and ammonium by the seagrass Posidonia oceanica, its leaf epiphyte community, the brown macroalgae Halopteris scoparia and the suspended particulate organic matter (SPOM). In Revellata Bay (Gulf of Calvi, Western Corsica), which is a very nutrient-poor region, the specific uptake rates (V) (μg N g N⁻¹ h⁻¹) of SPOM measured at ambient concentrations are 10-1000 higher than those of benthic primary producers. Macroalgae have intermediary V, between the seagrass leaf and leaf epiphytes. V are quite variable and the reasons for this variability remain unclear.Despite the difference of specific uptake rates found between benthic and pelagic primary producers, when integrating the uptake fluxes for a water column of 10 m depth, the contribution of benthic primary producers to N uptake fluxes (g N m⁻² h⁻¹) is significant, corresponding on average to 40% of total uptake flux. This results from the dominance in terms of N biomass of benthic primary producers in this shallow nutrient-poor area. When reported for the entire volume of the Revellata Bay, the contribution of benthic primary producers is reduced to 5-10% of total N uptake flux.Although this contribution could appear relatively low, it results in a significant direct transfer of inorganic nitrogen from the water column to the benthic compartment. By this transfer, the benthic plants act as a biological pump incorporating the pelagic N into the benthic compartment for a time longer than the characteristic time of phytoplankton dynamics (month-years vs. day-week).     

A NEW RECORD OF THE NUDIBRANCH GASTROPOD POLYCERA HEDGPETHI MARCUS, FROM THE INDIAN OCEAN OF SOUTH AFRICA

Polycera hedgpethi Marcus, 1964, previously known only fromthe Pacific coasts of California and Mexico, is recorded fromPlettenberg Bay, South Africa. The high degree of morphologicalconsistency betweeen Pacific and Indian Ocean material insuresthat they are conspecific. P. hedgpethi is readily distinguishablefrom P. capensis, the only other Polycera recorded from SouthAfrican waters. (Received 20 July 1980;     

Copepod populations during the spring bloom in an Alaskan subarctic embayment

Copepod population and biomass was monitored in Auke Bay, Alaska,during the spring bloom from 1987 to 1989. The most abundantspecies were Pseudocalanus spp., Oithona similis and Centropagesabdominalis, with Acartia clausi reaching high concentrationsin the surface waters. Although populations of Pseudocalanuswere similar during all three years, C.abdominalis and O.similisconcentrations were significantly higher in 1988 and lower in1989 than in 1987. The population differences may have resultedfrom warmer temperatures during early spring in 1988. Substantialcontributions to biomass resulted from advection of adult Calanusmarshallae and Metridia ochotensis and late stage Neocalanusplumchrus into the bay. While copepod populations in Auke Bayappear to be more sensitive to factors influencing the timingand development rate of various cohorts, biomass is substantiallyaltered by water mass movements.     

Effect of permanent sea ice cover and different nutrient regimes on the phytoplankton succession of fjords of the Vestfold Hills Oasis, eastern Antarctica

Early season phytoplankton communities in both Omega and TaynayaBays are characterized by diatoms sedimenting out of the overlyingsea ice. Initial nitrate, phosphate and silicate levels arehigh and the bay waters are covered with ice and well mixed.In Taynaya Bay the ice cover is retained throughout the seasonwhile Omega Bay is ice free for 6–8 weeks. After ice breakout in Omega Bay, the phytoplankton community changes from onedominated by diatoms to one dominated by the phytoflagellates,Pyramimonas spp., Cryptomonas sp. and Gymnodinium sp. In TaynayaBay the ice remained and even though phytoflagellates becamemore common, diatoms still dominated. These differences in communitycomposition result from differences in light climate, extentof stratification and nutrient levels.     

SOME OBSERVATIONS ON THE DIET AND DISTRIBUTION OF NUDIBRANCHS AT SIGNY ISLAND, ANTARCTICA

Observations were made on the diet and distribution of eightspecies of nudibranchs found in Borge Bay, Signy Island, Antarctica.Specimens from seven sites were examined in situ on four separateoccasions during 1992 and 1993 using SCUBA. A small collectionfor identification was also made Six of the eight species presentwere identified, and the first ecological data for at leastone species (Charcotia granulosa) were recorded. Notaeolidiagigas was feeding principally on hydroids of the genus Tubulariaover the entire depth range surveyed (3–36 m), and wasmost abundant in shallow water, whereas Truomella belli wasonly found at deeper sites, mostly on an octocoral of the genusAscolepis. Charcoaa granulosa and Pseudotritoma gracilidensappeared to be specialist bryozoan feeders and, as has beenfound at other locations, Austrodoris kerguelenesis specialisedon the demosponge Dendnlla antarcnca. Two unidentified aeolidspecies occurred almost entirely on particular hydroids andthe prey of Tritonia antarctica was not apparent. The physicalsize of Antarctic nudibranchs may have important implicationsto the type of prey and feeding strategy used by different species. (Received 11 May 1995; accepted 3 December 1995)     

Resources and possibilities for exploitation of North Adriatic seaweeds

Suggestions for a small-scale exploitation of seaweeds in the northern Adriatic are given along with a survey of the fresh weight biomass and chemical composition of individual species. The intertidal is occupied by Fucus virsoides. In polluted sites, it is replaced by seasonal annuals. Cystoseira species are dominant in the upper subtidal and represent the major part of seaweed resources in this area. In polluted sites they are replaced by Halopteris scoparia and Dictyota dichotoma. Peaks in biomass were found in spring in the upper water layers and in early summer lower in the subtidal. The protein content of most species exhibited maxima in spring. Elevated values were found in plants from polluted and estuarine habitats.     

Protoceratium reticulatum in northern Japan: environmental factors associated with seasonal occurrence and related contamination of yessotoxin in scallops

In 2003, an occurrence of the yessotoxin (YTX)-producing dinoflagellate,Protoceratium reticulatum, and resultant toxin concentrationin scallops was monitored in Okkirai Bay, northern Japan. Theoccurrence peaked after 1 July and reached a maximum density(400 cells L^–1) on 16 July. It occurred over a wide rangeof water temperature and inorganic nutrient concentrations andwas tolerant of a broad range of environmental conditions. Hydrologicalparameters were monitored, and it was obvious that P. reticulatumflourished under low salinity (30.59–32.60) and occurredat highest density in the surface layer (0–5 m depth)where effects from rainfall were greatest. In addition, dinoflagellatedensity increase and decrease was well correlated with inflowsof oceanic water into the bay. Thus, it can be assumed thatthe oceanic inflows may cause initial population increases (e.g.excystment or input of a ‘seed population’), withresultant growth in rain-affected waters and subsequent spreadthroughout the entire bay via water movement. YTX and 45-OHYTXconcentrations in scallops reached maximum levels (0.79 µgg^–1 and 0.44 µg g^–1 of digestive gland, respectively)2 weeks after the maximum cell density of P. reticulatum, andhigh levels of the toxin continued for a month. Low levels ofthe toxin were detected even during periods when cells werenot observed.     

THE AMINO ACID COMPOSITION OF FRESHWATER MOLLUSC SHELLS IN RELATION TO PHYLOGENY AND ENVIRONMENT

Quantitative thin layer chromatography of structural amino acidswas standardized for the study of shell proteins of 13 speciesof freshwater mollusc. There was slight intraspecific variationbetween individuals, particularly for tyrosine concentrations.No external periostracum was chemically identifiable in theshell of Lymnaea peregra (Müller) and this species showedsome amino acid heterogeneity in different parts of the shell.Despite these intraspecific variations, analysis of variancesuggested interspecific variation in concentrations for almostall the amino acids tudied. Cluster and principal componentsanalysis indicated that the amino acid composition did reflectphylogenetic affinity but that environmental factors were probablymore-important. (Received 5 August 1982; revised 5 August 1982;     

MICRURGICAL STUDIES IN CELL PHYSIOLOGY : I. THE ACTION OF THE CHLORIDES OF NA,K, CA,AND MG ON THE PROTOPLASM OF AM?BA PROTEUS.

By means of micro-dissection and injection Amœba proteus was treated with the chlorides of Na, K, Ca, and Mg alone, in combination, and with variations of pH. I. The Plasmalemma. 1. NaCl weakens and disrupts the surface membrane of the ameba. Tearing the membrane accelerates the disruption which spreads rapidly from the site of the tear. KCl has no disruptive effect on the membrane but renders it adhesive. 2. MgCl₂ and CaCl₂ have no appreciable effect on the integrity of the surface membrane of the ameba when applied on the outside. No spread of disruption occurs when the membrane is torn in these salts. When these salts are introduced into the ameba they render the pellicle of the involved region rigid. II. The Internal Protoplasm. 3. Injected water either diffuses through the protoplasm or becomes localized in a hyaline blister. Large amounts when rapidly injected produce a "rushing effect". 4. HCl at pH 1.8 solidifies the internal protoplasm and at pH 2.2 causes solidification only after several successive injections. The effect of the subsequent injections may be due to the neutralization of the cell-buffers by the first injection. 5. NaCl and KCl increase the fluidity of the internal protoplasm and induce quiescence. 6. CaCl₂ and MgCl₂ to a lesser extent solidify the internal protoplasm. With CaCl₂ the solidification tends to be localized. With MgCl₂ it tends to spread. The injection of CaCl₂ accelerates movement in the regions not solidified whereas the injection of MgCl₂ induces quiescence. III. Pinching-Off Reaction. 7. A hyaline blister produced by the injection of water may be pinched off. The pinched-off blister is a liquid sphere surrounded by a pellicle. 8. Pinching off always takes place with injections of HCl when the injected region is solidified. 9. The injection of CaCl₂ usually results in the pinching off of the portion solidified. The rate of pinching off varies with the concentration of the salt. The injection of MgCl₂ does not cause pinching off. IV. Reparability of Torn Surfaces. 10. The repair of a torn surface takes place readily in distilled water. In the different salt solutions, reparability varies specifically with each salt, with the concentration of the salt, and with the extent of the tear. In NaCl and in KCl repair occurs less readily than in water. In MgCl₂ repair takes place with great difficulty. In CaCl₂ a proper estimate of the process of repair is complicated by the pinching-off phenomenon. However, CaCl₂ is the only salt found to increase the mobility of the plasmalemma, and this presumably enhances its reparability. 11. The repair of the surface is probably a function of the internal protoplasm and depends upon an interaction of the protoplasm with the surrounding medium. V. Permeability. 12. NaCl and KCl readily penetrate the ameba from the exterior. CaCl₂ and MgCl₂ do not. 13. All four salts when injected into an ameba readily diffuse through the internal protoplasm. In the case of CaCl₂ the diffusion may be arrested by the pinching-off process. VI. Toxicity. 14. NaCl and KCl are more toxic to the exterior of the cell than to the interior, and the reverse is true for CaCl₂ and MgCl₂. 15. The relative non-toxicity of injected NaCl to the interior of the ameba is not necessarily due to its diffusion outward from the cell. 16. HCl is much more toxic to the exterior of a cell than to the interior; at pH 5.5 it is toxic to the surface whereas at pH 2.5 it is not toxic to the interior. NaOH to pH 9.8 is not toxic either to the surface or to the interior. VII. Antagonism. 17. The toxic effects of NaCl and of KCl on the exterior of the cell can be antagonized by CaCl₂ and this antagonism occurs at the surface. Although the lethal effect of NaCl is thus antagonized, NaCl still penetrates but at a slower rate than if the ameba were immersed in a solution of this salt alone. 18. NaCl and HCl are mutually antagonistic in the interior of the ameba. No antagonism between the salts and HCl was found on the exterior of the ameba. No antagonism between the salts and NaOH was found on the interior or exterior of the ameba. 19. The pinching-off phenomenon can be antagonized by NaCl or by KCl, and the rate of the retardation of the pinching-off process varies with the concentration of the antagonizing salt. 20. The prevention of repair of a torn membrane by toxic solutions of NaCl or KCl can be antagonized by CaCl₂. These experiments show directly the marked difference between the interior and the exterior of the cell in their behavior toward the chlorides of Na, K, Ca, and Mg.