Respiration as a function of oxygen concentration in intertidal barnacles

Respiration as a function of oxygen concentration was studied in two species of intertidal barnacles: Balanus amphitrite amphitrite ¹ (Darwin) and B. tintinnabulum tintinnabulum (L.). A critical oxygen tension was observed in both species below which the respiratory regulation broke down. In B. amphitrite amphitrite the critical oxygen tension was 2.5 ml O₂/l, and in B. tintinnabulum tintinnabulum 3.5 ml O₂/l. Species differences and habitat relations were observed in both species in their respiratory adaptation to oxygen concentration. B. amphitrite amphitrite which inhabits oxygen-deficient areas was able to regulate to much lower concentrations than B. tintinnabulum tintinnabulum which inhabits oxygen-rich open intertidal regions.     

Hypoxic life of intertidal acorn barnacles

Oxygen levels were monitored within the mantle cavities of three barnacle species ( Chthamalus stellatus, Semibalanus balanoides, Elminius modestus), using optode microsensors. Conditions were always hypoxic, even when barnacles were actively using the prosoma and cirri to pump aerated seawater into the mantle cavity. Mantle fluid oxygen concentrations were extremely variable; behaviour and oxygen concentrations were not closely coupled. Ventilation of the mantle cavity depended partially on external water flow, with higher and more stable mantle fluid oxygen concentrations being sustained when the water around barnacles was agitated. During emersion, barnacles initially pumped seawater between the mantle cavity and the cone above the opercular plates to achieve ventilation. As water was lost it was replaced by air bubbles, eventually resulting in an air-filled mantle cavity. In S. balanoides and E. modestus, once the mantle cavity was filled with air, the barnacle usually used up the oxygen within the bubble within 2–3 h and did not regain oxic conditions until the barnacle was reimmersed in seawater. In C. stellatus, the air bubble was repeatedly refreshed for many hours by pneumostome formation. In response to low environmental salinity, all three species closed the opercular plates firmly and rapidly used up oxygen within the mantle fluid.     

Desiccation stress in two intertidal beachrock biofilms

Chlorophyll a fluorescence was used to look at the effect of desiccation on the photophysiology in two beachrock microbial biofilms from the intertidal rock platform of Heron Island, Australia. The photophysiological response to desiccation differed between the beachrock microbial communities. The black biofilm from the upper shoreline, dominated by Calothrix sp., showed a response typical of desiccation-tolerant cyanobacteria, where photosynthesis closed down during air exposure with a rapid and complete recovery upon rehydration. In contrast, the pink biofilm from the mid-intertidal zone, dominated by Blennothrix sp., showed no distinct response to desiccation stress and instead maintained reduced photosynthesis throughout drying and re-wetting cycles. Spatial differences in photosynthetic activity within the black biofilm were evident with a faster recovery rate of photosynthesis in the surface cyanobacteria than in the deeper layers of the biofilm. There was no variation with depth in the pink biofilm. The photophysiological differences in desiccation responses between the beachrock biofilms exemplify the ecological niche specialisation of these complex microbial communities, where the functional differences help to explain their vertical distribution on the intertidal shoreline.     

Tolerance of high temperatures by some intertidal barnacles

The median lethal times of survival of the barnacles Elminius modestus, Balanus crenatus and B. balanoides, when continuously submerged at high temperatures, were determined for individuals collected in the summer and winter. In E. modestus and B. crenatus there was no seasonal change in high temperature tolerance. In B. balanoides, however, the adults were more susceptible in the winter than in the summer to temperatures a little below the upper lethal temperature. Using less comprehensive data for other British species of barnacles, it is concluded that, in general, the order of tolerance to high temperatures corresponds to the order of temperatures within the geographical and the intertidal distributions of the species. From the time-temperature-survival curves, intertidal barnacles are living closer to environmental temperatures than would be supposed on the basis of the measurement of the upper lethal temperature, which has been commonly measured for many species, but is of less ecological significance.     

Desiccation enhanced nitrogen uptake rates in intertidal seaweeds

Desiccation increased nitrate and ammonium uptake rates upon resubmergence in late summer populations of the intertidal macroalgae Gigartina papillata (C.Ag.) J.Ag., Enteromorpha intestinalis (L.) Grev., Fucus distichus L., and Pelvetiopsis limitata (Setch) Gardn. The ratio of nitrogen uptake rates in desiccated plants to rates in hydrated plants (controls) was correlated with the position of the species in the intertidal zone. Gracilaria pacifica Abbott., the species occurring at the lowest shore level, showed no enhancement of nitrogen uptake following desiccation. The high intertidal species such as P. limitata and F. distichus showed a two-fold enhancement of nitrate and ammonium uptake following more extensive desiccation (>30%) and continued uptake even following severe desiccation (50 to 60%). After the plants had been desiccated, the increase in nitrate uptake rates upon submergence lasted much longer than a similar enhancement of ammonium uptake. The duration of the enhanced nitrate uptake was similar to the time required for total rehydration but the uptake rates were not related to the state of rehydration. The potential contribution that this enhanced nitrogen uptake following desiccation could make to total nitrogen procurement for growth is discussed. The experiments were carried out in 1979 or 1980 and repeated in 1981.This paper is dedicated to Dr. R. F. Scagel on the occasion of his retirement for his outstanding contribution to phycology     

Parasitism can influence the intertidal zonation of non-host organisms

We investigated habitat utilization in Blainvilles beaked whale, Mesoplodon densirostris, in the northern Bahamas and, as such, this is the first analysis of fine-scale habitat utilization of any member of the genus Mesoplodon. We divided the area into 500×500 m grid squares and each square was assigned a classification for presence or absence of Blainvilles beaked whales, along with details of water depth, seabed gradient and seabed aspect. All squares where Blainvilles beaked whales occurred had gradients from 68 to 296 m/km and depths from 136 to 1,319 m and most faced northeast compared with 0–526 m/km, 10–3,000 m and all aspects for the whole study area. Generalized additive models and classification trees indicated that, in order of importance, aspect, gradient and depth were related to occurrence of Blainvilles beaked whales within the study area. We hypothesize that the relationships between habitat utilization and these topographic variables relates to the effects of interactions between a deepwater current and the seabed topography on preferred prey. Locally, prey animals may be concentrated in areas with a northeast aspect, intermediate gradients and depths between 200 and 1,000 m where the Deep Western Boundary Current is forced towards the surface by the local topography. These are the areas where Blainvilles beaked whales preferentially occurred.Communicated by O. Kinne, Oldendorf/Luhe     

Effects of settlement density on spatial arrangement in four intertidal barnacles

Balanus amphitrite was studied in an estuary (Halifax River) in central Florida from October to November 1990, while three other barnacle species were studied on the central coast (Monterey Bay) of California from April 1988 to July 1989. Mean nearest-neighbor distances indicated that in the majority of cases the spatial arrangement of settlers was random for three different balanomorph barnacles-B. amphitrite, B. glandula, and Chthamalus dalli. In Pollicipes polymerus, a lepidomorph species, strong aggregation among settlers was almost always observed. In the three balanomorph species there was no apparent relationship between settler density and the degree of aggregation. In P. polymerus there was a significant positive correlation between settler density and the degree of aggregation. Morphological differences between balanomorph and lepidomorph barnacles may influence the evolution of settlement behavior.     

A finite element method to solve a population dynamics stage-structured model of intertidal barnacles

Many marine organisms are fixed or highly sedentary as adults but the adult population may be strongly dependent on the oceanic transport of planktonic larvae. In order to assess interactions between oceanographic and biological processes that determine the population dynamics of marine organisms with a sessile adult phase restricted to the coastline and a planktonic larval phase, we present a stage-structured finite element model for the barnacle Balanus glandula that inhabits the rocky intertidal zone of central California, USA.     

Relationships between intertidal zonation and circatidal rhythmicity in littoral gastropods

The presence and phase of circatidal rhythmicity was correlated with vertical zonation and other ecological factors. Ten species were studied in the field and in aktographs under controlled conditions in the laboratory. Retina plicata, Melanerita atramentosa, Bembicium nanum, Austrocochlea obtusa and Morula marginalba occupied mid- or upper-littoral zonations, and were subjected to regular tidal influence. They were active at high water and for a period after the ebb, possibly as these were the times of least desiccation. Each possessed a circatidal activity rhythm under non-tidal conditions. Midlittoral Amphinerita polita and lower-littoral Theliostyla albicilla were active at low water, possibly because their prefered habitats reduced desiccation and other selective forces, for example wave action and predation, determined the phase of the rhythmicity. Supra- and upper-littoral Nodilittorina pyramidalis and Melarapha unifasciata and lower- and infralittoral specimens of Bembicium auratum displayed no overt circatidal rhythmicity, possibly because they were not subjected to regular tidal action.     

Post-larval development of two intertidal barnacles at elevated CO2 and temperature

Ocean acidification and global warming are occurring concomitantly, yet few studies have investigated how organisms will respond to increases in both temperature and CO₂. Intertidal microcosms were used to examine growth, shell mineralogy and survival of two intertidal barnacle post-larvae, Semibalanus balanoides and Elminius modestus, at two temperatures (14 and 19°C) and two CO₂ concentrations (380 and 1,000 ppm), fed with a mixed diatom-flagellate diet at 15,000 cells ml⁻¹ with flow rate of 10 ml⁻¹ min⁻¹. Control growth rates, using operculum diameter, were 14 ± 8 μm day⁻¹ and 6 ± 2 μm day⁻¹ for S. balanoides and E. modestus, respectively. Subtle, but significant decreases in E. modestus growth rate were observed in high CO₂ but there were no impacts on shell calcium content and survival by either elevated temperature or CO₂. S. balanoides exhibited no clear alterations in growth rate but did show a large reduction in shell calcium content and survival under elevated temperature and CO₂. These results suggest that a decrease by 0.4 pH_(NBS) units alone would not be sufficient to directly impact the survival of barnacles during the first month post-settlement. However, in conjunction with a 4–5°C increase in temperature, it appears that significant changes to the biology of these organisms will ensue.     

Phosphate uptake by intertidal algae in relation to zonation and season

The removal of phosphate from ambient seawater by whole plants of five species of fucoid algae, collected from the east coast of N. Ireland in 1988 and 1989, was followed over 6-h periods. A transient uptake pattern was observed forPelvetia canaliculata (L.) Dcne. et Thuret,Fucus spiralis L.,F. vesiculosus L. andF. serratus L., consisting of an initial period of high uptake, followed by a phase of zero uptake and then a period at an intermediate rate.Ascophyllum nodosum (L.) Le Jolis had a constant slow rate of uptake over 6 h. The initial uptake rate ofF. spiralis was significantly greater than that of any other species. Phosphate uptake over a 2-h period was measured at concentrations ranging from that of ambient seawater to 25µg-at. l^–1 for whole plants ofF. spiralis andF. serratus, using a large scale batch method. A small scale batch method was used for whole plants ofP. canaliculata and sections of the other four species investigated. Uptake abilities of the algae at low concentrations of phosphate were compared using the parameterV ₁ (the uptake rate at 1µg-at. l^–1) and at high concentrations usingV _max, the maximum uptake rate. These kinetic parameters of uptake were calculated using a method that avoids bias and permits statistical evaluation of the results. The fucoid algae studied could be divided into two distinct groups on the basis of their abilities to take up phosphate from seawater.P. canaliculata andA. nodosum had low values ofV ₁ in winter, which were also correlated with their positions on the shore and did not vary between winter and summer. TheFucus species had higher values ofV ₁ in winter, which were also correlated with their positions on the shore. In summer, however,V ₁-values for these species decreased and no longer correlated with their shore heights. TheV _max-value forF. spiralis was higher in winter than in summer but was signifcantly greater than that of any other species at all times of year. The ecological significance ofV _max is discussed in relation to nutrient limitation and the possible occurrence of patches of high nutrient concentration in the intertidal environment.     

Vertical zonation of endosymbiotic zooxanthellae within a population of the intertidal sea anemone,Anthopleura uchidai

Intertidal organisms commonly form zonation bands along the shore. Environmental stressors often determine the vertical position of each zonation band. These stressors may similarly affect the distribution pattern of endogenous species in their intertidal hosts. To evaluate this possibility, we investigated the distribution pattern of endosymbiotic zooxanthellae in the genus Symbiodinium in a population of the intertidal sea anemone Anthopleura uchidai. We used molecular genetics to identify the Symbiodinium clades and found that A. uchidai has two clades of Symbiodinium, clades A and F. These Symbiodinium clades were disproportionally distributed along the vertical gradient of the intertidal shore. Anemones on the upper shore exclusively possessed clade F Symbiodinium while clade A Symbiodinium became dominant in the sea anemones on the lower shore. Photosynthesis activity assays showed that these Symbiodinium clades had similar net productivities at 23.3 and 31.8 °C at all irradiance levels. At 35 °C, however, clade A Symbiodinium exhibited substantially lower net productivities than clade F Symbiodinium, demonstrating that these Symbiodinium clades have distinct tolerances to thermal stress. These results suggest that the thermal gradient across tidal height is a major factor shaping the zonation pattern of Symbiodinium clades in A. uchidai.     

Parasitism as a determinant of community structure on intertidal flats

The burrowing and movement ability of the New Zealand cockle Austrovenus stutchburyi is reduced when infected by echinostome trematodes. Previous experimental evidence from a single site suggests that this parasite-induced behavioural change of a key bivalve can affect the structure of the surrounding benthic community. By using multiple regression analyses on data collected from 17 intertidal flats, we here show that cockle parasitism is associated with macrozoobenthic community structure on a larger spatial scale. Regressions were performed for animal abundance, biomass, species diversity and species richness separately, entering cockle parasitism (infection intensity), presence/absence of ghost shrimps (Callianassa filholi), cockle density, primary producer abundance and organic content, particle size, sorting coefficient and gravel content of the substrate as predictors. Next to ghost shrimps, cockle parasitism was the best predictor of animal abundance by affecting (mainly positively) 8 of the 49 most widespread species significantly. Cockle parasitism was also associated with the biomass of anthozoans (positively), nemerteans (negatively) and bivalves (positively), whereas overall animal biomass was positively related to the sorting coefficient of the substrate. Species diversity was positively associated with cockle parasitism and gravel content of the substrate. Species richness was significantly associated with cockle parasitism (positively), ghost shrimps (negatively) and abundance of primary producers (positively) in combination. The impact of cockle parasitism on benthic community structure is believed governed directly or indirectly by (1) reduced sediment disturbance, (2) increased surface structural complexity and (3) availability of larval trematodes as an additional food source.     

Desiccation,higher temperatures and upper intertidal limits of three species of sea mussels (Mollusca: Bivalvia) in New Zealand

Distribution, abundance, and resistance adaptations to higher temperature and desiccation of three species of intertidal mussels (Mytilus edulis aoteanus, Perna canaliculus and Aulacomya maoriana) were studied in New Zealand. M. edulis aoteanus generally was more abundant upshore, with P. canaliculus dominating downshore. M. edulis aoteanus was more common than P. canaliculus on the outside of mixed-species clumps. Abundance of A. maoriana was variable, with individuals favouring damp habitats such as inside mussel clumps. In moving air at 75% relative humidity and at 20°C or 30°C, median lethal levels of water loss were similar for P. canaliculus and M. edulis aoteanus but lower for A. maoriana. Rates of desiccation varied inversely with size and were higher for P. canaliculus, due mainly to valve gaping with resultant loss of water from the mantle cavity. M. edulis aoteanus was more tolerant of higher water temperatures than were the other species. Success in colonizing upshore or more aerially exposed habitats seems to be related to ability of small mussels to tolerate desiccation, especially during hot, windy weather.     

Vertical swimming in wave-induced currents as a control mechanism of intertidal migration by a sand-beach isopod

Both the vertical and horizontal distributions ofEurydice pulchra (Leach) within the water column of the surf zone were recorded throughout complete tidal cycles on a sandy beach in North Wales during the summer of 1989. Upon emerging from the sand, the isopods tended to swim up in the water column, where transport onshore would be facilitated by the wave-induced, onshore currents which laboratory wave-tank experiments have confirmed to occur near the water surface. This combination of active and passive transport to the water's edge results in high numbers of individuals in the narrow swash zone. At and just after the time of high tide, individuals swim to the water/sediment interface where, as again confirmed by wave-tank experiments, the predominant water movement is offshore. Continued swimming near the bottom during the ebb tide before reburrowing in the sand ensures transport downshore and avoidance of stranding above the characteristic level of zonation on the shore. Vertical migrations ofE. pulchra in the water column permit differential exploitation of up and downshore currents to achieve horizontal migration.     

Significance of burrow-opening diameter as a flood-prevention mechanism for air-filled burrows of small intertidal arthropods

Small air-breathing terrestrial arthropods (e.g. beetles, ants, crabs) living within the intertidal zone of mud and sand flats construct burrows with a narrow opening to the substrate surface. Despite frequently remaining open, these burrows are not flooded by the incoming tide. We examine, from a theoretical standpoint, the rôle of burrow-opening diameter in preventing burrow flooding. We determine a critical burrow diameter of 3 mm above which burrows are likely to flood unless the entrance is plugged by the burrow's inhabitant(s) prior to tidal inundation. We examine water penetration via the burrow entrance and seepage through the burrow walls. A practical mathematical solution is provided which can be used to examine the extent to which water may penetrate a given animal burrow in the field.     

Stable carbon isotope ratios in Red Sea barnacles (Cirripedia) as an indicator of their food source

The stable isotope ratio ¹²C/¹³C was used to investigate the source of carbon in free-living barnacles and in coral-inhabiting barnacles from the Red Sea. The δ¹³C of most of the barnacles collected on the open shore ranges between −17.5 and −19.7‰, indicating relative enrichment of light carbon originating from the open-sea phytoplankton. Those collected in closed habitats showed heavier isotopic composition. The δ¹³C of the coral-inhabiting barnacles ranges from −14.1 to −16.7‰, suggesting that the carbon contribution of open-sea plankton to these barnacles is less important than it is to free-living barnacles. We hypothesize that coral organic matter and zooxanthellae expelled by the host coral contribute carbon to the barnacle, and that a mixture of this relatively heavy carbon with carbon from other sources is responsible for the high values of δ¹³C in coral barnacles. Received: 28 February 1997 / Accepted: 16 September 1997     

The environment as a factor of production

This paper uses firm-level data about electric utilities to develop an empirical model of how electric utilities use and bank SO₂ pollution permits under the Acid Rain Program. The empirical model considers emissions, fuels, and labor as variable inputs with quasi-fixed stocks of permits and capital. Consequently, substitution possibilities between the environment and other production factors can be measured and tested. The results reveal substantial substitution between emissions, permit stocks, capital, fuel, and labor. The empirical findings also indicate that firms bank permits primarily as a hedge against uncertainty and for other firm-specific reasons. Overall, the results suggest that cap-and-trade approaches can reduce the cost of meeting environmental goals by providing a mechanism for addressing regulatory and market risks and by signaling an appropriate price for factor use, especially irreversible capital investments.