INFLUENCE OF SALINITY ON THE FORM OF ASTEROCYTIS IN PURE CULTURE1

The growth form of an isolate of Asterocytis ornata in pure culture changed from filamentous in a full-strength seawater medium to a unicellular or bicellular form closely resembling the genus Chroothece in a medium of quarter-strength seawater. The alga did not grow in media of lower salinities, or in media in which seawater was replaced by KCl, NaCl, or CaCl₂. The formation of filaments from single cells could not be attributed to osmolarity. The controlling factors seemed to be the concentrations of cations, notably Na⁺ and Mg⁺⁺. However, the filaments produced experimentally in a defined medium, were never as extensively developed as those occurring in seawater, an indication that further studies should be done. The occurrence of the Asterocytis form, in freshwater habitats remains to be explained. There may be distinct physiological races, if not true species, within the genus.     

Occurrence of thermotolerant Campylobacter species in surface waters of a Mediterranean area and in its prevailing pollution sources

Aims: To determine the prevalence of Campylobacter in surface waters of a highly populated Mediterranean area. Methods and Results: Surface water and wastewater samples were collected from an area in the north‐east of Spain during a 2‐year study. All the samples were analysed using the MPN method and Multiplex PCR to quantify and identify Campylobacter. It was detected in 82% of the samples from the Llobregat River with a mean of 1·3 MPN 100 ml^?1. The lowest counts were obtained in summer. Campylobacter coli was the predominant species in this river. The bacteria were isolated from marsh water but not from seawater samples. The highest counts of campylobacters were found in poultry wastewater where Camp. jejuni was the predominant species, as in urban sewage. In pig slurry, Camp. coli was the only species detected. Conclusions: Campylobacter jejuni and Camp. coli are present and widely distributed in the surface water of the studied area. The two species co‐exist, with Camp. coli being predominant. In river water, campylobacter counts presented a seasonal distribution. No relationship with faecal indicators was found. Significance and Impact of the Study: This study provides the first data on the occurrence and concentrations of thermotolerant campylobacter species in surface water in a Mediterranean area.     

Survival ofLegionella pneumophila in the aquatic environment

Survival ofLegionella pneumophila SG 1 in seawater and river water was assessed using plate counts on buffered charcoal yeast extract agar amended with α-ketoglutarate (BCYEα) and [³H]thymidine-labeling. The [³H]thymidine-labeling method for assessing survival ofL. pneumophila in aquatic environments was compared with viable counts, direct fluorescent microscopy (DFA), and acridine orange direct counts (AODC). Protozoa were isolated from the samples employed in the study and identified by characteristic trophozite and cyst morphology. Selective filtration employing 2.0 μm Nucleopore filters was used to determine the effect of grazing on survival ofL. pneumophila in seawater and river water.Legionella viability as measured by plate counts (CFU/ml), declined to a greater extent than cell lysis, assessed by thymidine, DFA, and AODC counts, suggesting thatL. pneumophila survives in aquatic habitats to a greater extent than revealed through culturable counts.     

DEVELOPMENTAL STUDIES ON THE COENOCYTIC ALGA, CAULERPA SERTULARIOIDES

Thallus growth and development in the coenocyti alga Caulerpa sertularioides (Gmelin) Howe have been studied quantitatively. In unsupplemented seawater at 26 C and in a 12:12 hr light/dark cycle, new rhizomes formed near the old growing points on thalli transplanted from the ocean. Adjacent to the apices of new rhizomes, rhizoids were produced downward, regularly spaced and at a rate of about 1.5/day. Upright. shoots developed irregularly in acropetal succession behind the tips of either the parent or the new rhizomes, which arose as branches of the old. Rates of rhizome, rhizoid, and upright shoot elongation were 0.4, 0.81, and 0.54 cm/day, respectively. Thalli survived up to 2 months in unsupplemented seawater. Long-term growth was obtained by varying culture conditions. A substratum of sand, apparently rich in microorganisms, produced long-term thallus growth in seawater, and the form of development changed so that upright shoot formation was promoted and rhizome elongation halved. Similar effects were elicited by indole-3-acetic acid, 5 × 10^-5, M in seawater and by sap expressed from C. racemosa or C. sertularioides and added to seawater at 2.5–10% by volume. The regulation of development in an algal coenocyte is discussed and analogies with regulation in multicellular plants are drawn.     

Dynamics of bacterial populations during bench‐scale bioremediation of oily seawater and desert soil bioaugmented with coastal microbial mats

This study describes a bench‐scale attempt to bioremediate Kuwaiti, oily water and soil samples through bioaugmentation with coastal microbial mats rich in hydrocarbonoclastic bacterioflora. Seawater and desert soil samples were artificially polluted with 1% weathered oil, and bioaugmented with microbial mat suspensions. Oil removal and microbial community dynamics were monitored. In batch cultures, oil removal was more effective in soil than in seawater. Hydrocarbonoclastic bacteria associated with mat samples colonized soil more readily than seawater. The predominant oil degrading bacterium in seawater batches was the autochthonous seawater species Marinobacter hydrocarbonoclasticus. The main oil degraders in the inoculated soil samples, on the other hand, were a mixture of the autochthonous mat and desert soil bacteria; Xanthobacter tagetidis, Pseudomonas geniculata, Olivibacter ginsengisoli and others. More bacterial diversity prevailed in seawater during continuous than batch bioremediation. Out of seven hydrocarbonoclastic bacterial species isolated from those cultures, only one, Mycobacterium chlorophenolicum, was of mat origin. This result too confirms that most of the autochthonous mat bacteria failed to colonize seawater. Also culture‐independent analysis of seawater from continuous cultures revealed high‐bacterial diversity. Many of the bacteria belonged to the Alphaproteobacteria, Flavobacteria and Gammaproteobacteria, and were hydrocarbonoclastic. Optimal biostimulation practices for continuous culture bioremediation of seawater via mat bioaugmentation were adding the highest possible oil concentration as one lot in the beginning of bioremediation, addition of vitamins, and slowing down the seawater flow rate.     

FLUORESCENCE INDUCTION AND PHOTOSYNTHETIC RESPONSES OF ARCTIC ICE ALGAE TO SAMPLE TREATMENT AND SALINITY1

The measurement of Photosynthetic rates of algae growing on the undersurface of 1. 7 m thick ice in the Canadian Arctic (Resolute Passage. N.W.T.) presents several problems. During the preparation of samples for physiological measurements, the ice algae may he exposed to salinity and temperature shocks. Fluorescence induction (the rise in in vivo Chl a fluorescence intensity during a period of millineconds) and photosynthesis-irradiance (PI) experiments examined the potential effects of salinity and temperature on the physiology of ice algae. Experimental suspensions were routinely prepared by scraping one part ire crystals (11–14%₀ salinity) and attached algae from the bottom ice into four parts filtered seawater (32%₀ salinity). giving a final salinity of 28–31%₀. Post-dilution of melted ice scrapings with seawater suppressed photosynthetic ¹⁴C-fixation and decreased A_DCMU (the area above the fluorescence induction curve measured in the presence of the inhibitor DCMC: an estimate of photosynthetic capacity) by a factor of 3–16. due to the low salinity of the melted ice scrapings. Fluorescence induction and PI experiments showed that the ice algae had a salinity optimum near 30%₀, close to the ambient seawater salinity, Experiments in which the Chl a concentration was manipulated showed that A_DCMU, P^a_m (Chl a-normalized rate of photosynthesis at light saturation), and a (photosynthetic efficiency) declined with increasing Chl a concentration. Ice algae tolerated heating (l.5°C-min^-1) up to 17° C, above which A_DCMU’decreased with sample temperature.     

EFFECTS OF TEMPERATURE AND ILLUMINANCE ON CELL DIVISION RATES OF THREE SPECIES OF TROPICAL OCEANIC PHYTOPLANKTON1

Three species of tropical oceanic phytoplankton were isolated from two locations in the eastern Pacific Ocean. Unialgal cultures were maintained in an enriched seawater medium. The effects of temperature, and, in separate experiments, illuminance, on the exponential cell division rates of those algae were investigated. For 2 isolates of Gymnodinium sp. (probably G. simplex), maximum growth rates were 1.25 and 1.7 divisions/24 hr, the optimum temperature range was 23–29 C, the compensation illuminance was 35 ft-c, and the saturation illuminance was 750 ft-c and above. For a small species of Chaetoceros, the maximum growth rate was 6.0 divisions/24 hr, the optimum temperature range was 23–37 C, the compensation illuminance was 10 ft-c, and the saturation illuminance was 600 ft-c. For a small Nannochloris species, the maximum growth rate was 4.5 divisions/ 24 hr, the optimum temperature range was 27–37 C, and the saturation illuminance was 800 ft-c. Nannochloris grew heterotrophically by apparently utilizing organic matter supplied by soil extract.     

Characterization of tetracycline resistance genes in tetracycline-resistant Enterobacteriaceae obtained from a coliform collection

Tetracycline resistance has been used as the key determinant to monitor resistance genes in natural environments such as rivers, lakes or seawater. The aim of this study was evaluate the frequency of tetA, tetB, tetC, tetD and tetE genes in 52 tetracycline-resistant Enterobacteriacea isolated from river water in the North East Black Sea Region of Turkey. In 52 tetracycline-resistant strains, resistance was mediated by tetA in eight (15.3%) strains, tetB in ten (19.2%) strains and both tetA and tetB in one (1.9%) strain. No tetC, tetD or tetE-mediated resistance was detected. In conclusion, the river water may be considered as a reservoir for the antibiotic resistance genes and the people living in this area may be under risk. To our knowledge, this is the first report for molecular characterization of tetracycline resistance in Enterobacteriaceae of river water origin in Turkey.     

Phytoplankton community diversity is influenced by environmental factors in the coastal East China Sea

Surface seawater was collected in four different seasons in the coastal East China Sea adjacent to the Yangtze River Estuary and phytoplankton community diversity was analysed using rbcL genetic markers. Phytoplankton diversity (Shannon Index) was found to be highest in autumn and lowest in summer, which was mainly controlled by seawater temperature, river runoff, the Taiwan Warm Current and possibly other environmental factors. For taxa characterized by Form IAB rbcL, the abundance of Chlorophyta was much greater than those of Proteobacteria and Cyanobacteria throughout the year with the most dominant taxa being Bathycoccus prasinos (Chlorophyta) in spring and Micromonas sp. (Chlorophyta) in other seasons. For taxa identified by Form ID rbcL, Coscinodiscophyceae (diatoms) constituted the largest group (most clones) in the phylogenetic tree. Dinophysis fortii (a dinoflagellate) was found to be the most abundant species in winter and spring and Skeletonema spp. (a diatom) dominated the phytoplankton community in summer and autumn. The seasonal dominance of Dinophysis fortii agreed well with the recently increasing proportion of dinoflagellates in the phytoplankton community in the coastal East China Sea. The abundance of Dinophysis fortii was negatively correlated with seawater temperature, suggesting that harmful algal blooms caused by this species may primarily occur in spring.     

INORGANIC CARBON LIMITATION OF PHOTOSYNTHESIS IN ULVA ROTUNDATA (CHLOROPHYTA)1

A computerized oxygen electrode Astern was used to make rapid and accurate measurements of photosynthetic light and dissolved inorganic carbon (DIC) response cures with a macroalga. Ulva rotundata Blid. was grown in an outdoor, continuous flow system in seawater under sunlight or 9% of sunlight at Beaufort, North Carolina. The light compensation points in the shade- and sun-grown plants, measured in seawater, were at photon flux densities (PFDs) of 16 and 27 μmol. Photons·m^?2·s^?1, respectively but the quantum yield of O₂ evolution was not significantly different. Rates of photosynthesis in seawater per unit area of thallus under saturating light and rates of dark respiration were about 1.5-fold higher in sun- than in shade-grown plants. The concentration of DIC in seawater (approximately 2 mM) limited photosynthesis at absorbed PFDs above 60–70 μmol photons·m^?2·s^?1 Addition of 20 mM inorganic carbon had no effect on quantum yield but caused about a 1.5-fold increase in the light-saturated photosynthetic rate in both shade- and sun-grown Ulva. The effect of DIC supplementation was greatest in plants grown in October and least in plants grown in June. The light- and DIC-saturated rate of photosynthesis in seawater was similar to the maximum rate obtained by exposing Ulva to 10% CO₂, in the gas phase. The carbon isotope values (δ¹³C, reflecting the ¹³C/¹²C ratio compared to a standard) of Ulva grown in the same seawater supply were dependent on light and agitation. Samples from Beaufort Inlet were more negative (δ¹³C value, ?20.03‰) than those grown in bright light with agitation (δ¹³C value, ?17.78‰ outdoors; ?17.23‰ indoors), which may indicate DIC supply limited carbon uptake in seawater.     

Contrasting patterns of genetic structure and phylogeography in the marine agarophytes Gelidiophycus divaricatus and G. freshwateri (Gelidiales,Rhodophyta) from East Asia

The evolutionary and population demographic history of marine red algae in East Asia is poorly understood. Here, we reconstructed the phylogeographies of two upper intertidal species endemic to East Asia, Gelidiophycus divaricatus and G. freshwateri. Phylogenetic and phylogeographic inferences of 393 mitochondrial cox1, 128 plastid rbcL, and 342 nuclear ITS2 sequences were complemented with ecological niche models. Gelidiophycus divaricatus, a southern species adapted to warm water, is characterized by a high genetic diversity and a strong geographical population structure, characteristic of stable population sizes and sudden reduction to recent expansion. In contrast, G. freshwateri, a northern species adapted to cold temperate conditions, is genetically relatively homogeneous with a shallow population structure resulting from steady population growth and recent equilibrium. The overlap zone of the two species roughly matches summer and winter isotherms, indicating that surface seawater temperature is a key feature influencing species range. Unidirectional genetic introgression was detected at two sites on Jeju Island where G. divaricatus was rare while G. freshwateri was common, suggesting the occurrence of asymmetric natural hybrids, a rarely reported event for rhodophytes. Our results illustrate that Quaternary climate oscillations have left strong imprints on the current day genetic structure and highlight the importance of seawater temperature and sea level change in driving speciation in upper intertidal seaweed species.     

Marine hydrocarbonoclastic bacteria as whole‐cell biosensors for n‐alkanes

Whole‐cell biosensors offer potentially useful, cost‐effective systems for the in‐situ monitoring of seawater for hydrocarbons derived from accidental spills. The present work compares the performance of a biosensor system for the detection of alkanes in seawater, hosted in either Escherichia coli (commonly employed in whole‐cell biosensors but not optimized for alkane assimilation) or different marine bacteria specialized in assimilating alkanes. The sensor system was based on the Pseudomonas putida AlkS regulatory protein and the PalkB promoter fused to a gene encoding the green fluorescent protein. While the E. coli sensor provided the fastest response to pure alkanes (25‐fold induction after 2 h under the conditions used), a sensor based on Alcanivorax borkumensis was slower, requiring 3–4 h to reach similar induction values. However, the A. borkumensis sensor showed a fourfold lower detection threshold for octane (0.5 μM), and was also better at sensing the alkanes present in petrol. At petrol concentrations of 0.0125%, the A. borkumensis sensor rendered a sevenfold induction, while E. coli sensor showed no response. We discuss possible explanations to this behaviour in terms of the cellular adaptations to alkane uptake and the basal fluorescence produced by each bacterial strain, which was lowest for A. borkumensis.     

Leucine‐to‐carbon empirical conversion factor experiments: does bacterial community structure have an influence?

The suitability of applying empirical conversion factors (eCFs) to determine bacterial biomass production remains unclear because seawater cultures are usually overtaken by phylotypes that are not abundant in situ. While eCFs vary across environments, it has not been tested whether differences in eCFs are driven by changes in bacterial community composition or by in situ environmental conditions. We carried out seawater cultures throughout a year to analyse the correlation between eCFs and bacterial community structure, analysed by catalysed reporter deposition fluorescence in situ hybridization. Gammaproteobacteria usually dominated seawater cultures, but their abundance exhibited a wide range (25–73% of cell counts) and significantly increased with inorganic nutrient enrichment. Flavobacteria were less abundant but increased up to 40% of cells counts in winter seawater cultures, when in situ chlorophyll a was high. The correlations between eCFs and the abundance of the main broad phylogenetic groups (Gamma‐, Alphaproteobacteria and Flavobacteria) were significant, albeit weak, while more specific groups (Alteromonadaceae and Rhodobacteraceae) were not significantly correlated. Our results show that the frequent development of the fast‐growing group Alteromonadaceae in seawater cultures does not strongly drive the observed variations in eCFs. Rather, the results imply that environmental conditions and the growth of specific phylotypes interact to determine eCFs.     

长江宜昌段桥边河大型底栖动物功能摄食类群时空分布特征

研究河流生境时空变化对大型底栖动物功能摄食类群的影响,分析底栖动物功能摄食类群对环境因子的响应关系,对评估河流生态系统健康具有重要意义。以长江支流桥边河为研究对象,基于2020年8月、2021年1月和2021年4月对桥边河大型底栖动物和水体理化因子的调查数据,分析了大型底栖动物功能摄食类群的构成以及时空分布特征。结果表明：共采集到大型底栖动物3门38种,包括节肢动物门23种、软体动物门13种、环节动物门2种。桥边河大型底栖动物功能摄食类群中滤食者占绝对优势,其次为刮食者、捕食者、撕食者和收集者。滤食者的优势种为闪蚬和河蚬,刮食者的优势种为方格短沟蜷、铜锈环棱螺和卵萝卜螺,捕食者的优势种为河蟌,撕食者的优势种为秀丽白虾,收集者的优势种为黄色羽摇蚊。冗余分析（RDA）表明,影响桥边河大型底栖动物功能摄食类群的主要环境因子为溶解氧（DO）、氨态氮（NH₄⁺-N）、水深（Dep）、pH、温度（T）和硝态氮（NO₃^--N）。研究大型底栖动物功能摄食类群组成和时空分布特征,可为河流生态系统修复提供参考依据。     

Salinity tolerance in some mangrove species from Pakistan

Growth, ionic and water relations of three mangrove species viz. Avicennia marina, Ceriops tagal and Rhizophora mucronata werestudied in different seawater concentrations (0, 25, 50, 75 and 100%).All mangrove species showed optimal growth at 50% seawater. Relativelymore biomass was accumulated by R. mucronata while C. tagalhad the tallest individuals. Tissue water potential became more negativewith the increase in salinity and stomatal conductance was decreased in allplants. Higher stomatal conductance was noted in R. mucronata,followed by A. marina and C. tagal. Sodium and chloride ionsincreased with the increase in salinity and this accumulation was muchhigher in A. marina.     

THE ROLE OF THE REACTIVITY AND CONTENT OF IRON OF AEROSOL DUST ON GROWTH RATES OF TWO ANTARCTIC DIATOM SPECIES1

The atmosphere is widely recognized as a major source of Fe in the form of iron‐containing dust. This study provides the first experiments in which the impact of dust on the growth rates of single species of Antarctic diatoms was assessed under laboratory conditions. The dust was among others characterized by x‐ray powder diffraction analysis, analysis of total and amorphous Fe content, and dissolution rates of Fe in seawater. The amount of bioavailable Fe from the dust was determined, not via the complicated chemistry of Fe in seawater but by using diatoms as bioindicators for available Fe. Cultures of two large diatom species, Actinocyclus sp. and Thalassiosira sp., were amended with potential dust aerosols from two dust‐supplying regions, Namibia and Mauritania, and responses on growth rates were monitored. Apart from a difference in total Fe content, a difference in crystallinity existed in the Fe minerals of both dust types. The fraction of amorphous Fe was reflected in a higher reactivity/dissolution of Fe in seawater. The increase in growth rate upon dust addition was positively related with the amount of amorphous Fe in the dust and with the dissolution rate of Fe in seawater. However, compared with equal FeCl₃ concentrations, the dissolved Fe from the dust was not completely available for the diatoms. Interestingly, the diatoms used only a small part of the dissolved Fe, demonstrating the importance of algae as bioindicators.     

Novel function of eubacterial flagella: role in aggregation of a marine bacterium

Pseudomonas marina (ATCC 27 129) rapidly aggregates when suspended in buffered artificial seawater (ASW). Light microscopic observations of stained preparations, showed that flagella-flagella contact was responsible for this phenomenon. Aggregation did not occur if flagella were sheared off, or if motility was inhibited with NaN₃. Aggregates were not observed when Mg²⁺ was omitted from ASW, even though the bacteria remained motile. Other divalent cations, including Ca²⁺, Mn²⁺, and Ba²⁺ could replace Mg²⁺. However, there is no absolute requirement for divalent cations, since aggregation occurred in ASW containing Cs⁺ or Li⁺ instead of Mg²⁺. P. marina aggregates developed from pH 5.8–8.4, but not below pH 5.8 even though motility continued unimpaired to pH 4.5.Abbreviation ASW artificial seawater     

Effect of parental mate choice and semi‐natural early rearing environment on the growth performance and seawater tolerance of Chinook salmon Oncorhynchus tshawytscha

To assess whether parental mate choice and early rearing in a semi‐natural spawning channel may benefit the culture of Chinook salmon Oncorhynchus tshawytscha, 90 day growth trials were conducted using hatchery O. tshawytscha (hatchery), mate choice O. tshawytscha (i.e. the offspring of parents allowed to choose their own mate) that spent 6 months in a spawning channel prior to hatchery rearing (channel) and mate choice O. tshawytscha transferred to the hatchery as fertilized eggs (transfer). During the growth trials, all O. tshawytscha stocks were reared separately or in either mixed channel and hatchery or transfer and hatchery groups for comparison of performance to traditional practices. After 60 days in fresh water, all O. tshawytscha were transferred to seawater for an additional 30 days. Reared separately, all stocks grew c. 4·5 fold over 90 days but specific growth rate (G) and food conversion efficiency were higher in fresh water than after seawater transfer on day 60. In contrast, hatchery O. tshawytscha from mixed hatchery and channel and hatchery and transfer growth trials had a larger mass and length gain than their counterparts on day 60, but reduced G in seawater. In general, plasma levels of growth hormone, insulin‐like growth factor I and cortisol did not differ among any O. tshawytscha groups in either the separate or mixed growth trials. Despite some differences in gill Na⁺,K⁺‐ATPase activity, all O. tshawytscha had a high degree of seawater tolerance and experienced virtually no perturbation in plasma chloride following seawater transfer. Overall, all O. tshawytscha exhibited similar growth and seawater performance under traditional hatchery conditions and any benefit derived from either parental mate choice or semi‐natural early rearing environment was only observed in the presence of mutual competition with hatchery O. tshawytscha.     

Overcoming the production limitations of Photorhabdus temperata ssp. temperata strain K122 bioinsecticides in low-cost medium

For low-cost production of Photorhabdus temperata ssp. temperata strain K122 bioinsecticide, a cheap complex medium was optimized. Diluted seawater was used as the source of micronutrients, especially sodium chloride, involved in the improvement of cell density, culturability and oral toxicity of the bacterium P. temperata against Ephestia kuehniella larvae. Thus, the new formulated medium was composed only of 10 g/l of soya bean meal, used as the carbon and nitrogen main source, mixed in sevenfold diluted seawater. At such conditions, several limitations of P. temperata bioinsecticide productions were shown to be overcome. The appearance of variants small colony polymorphism was completely avoided. Thus, the strain K122 was maintained at the primary form even after prolonged incubation. Moreover, the viable but nonculturable state was partially overcome, since the ability of P. temperata cells to form colonies on the solid medium was prolonged until 78 h of incubation. In addition, when cultured in the complex medium, P. temperata cells were produced at high cell density of 12 × 10⁸ cells/ml and exhibited 81.48% improvement of oral toxicity compared to those produced in the optimized medium. With such medium, the large-scale bioinsecticides production into 3-l fully controlled fermenter improved the total cell counts, CFU counts and oral toxicity by 20, 5.81 and 16.73%, respectively. This should contribute to a significant reduction of production cost of highly potent P. temperata strain K122 cells, useful as a bioinsecticide.     

Controlled activation of species typical behaviour to low salinity,seawater movement and seawater depth in <Emphasis Type="Italic">Aurelia labiata</Emphasis> (Scyphozoa) Jellyfish in Roscoe Bay,Canada

Controlled observations in Roscoe Bay examined whether Aurelia labiata medusae would respond to three environmentally significant stimuli: low salinity, seawater movement and seawater depth. Significantly more upward-swimming medusae turned and swam down or sideways when they encountered an experimentally created low-salinity plume than did upward-swimming medusae that encountered a seawater plume or a seawater plume containing milk powder. Downward-swimming medusae that encountered a plume containing freshwater continued swimming down. Significantly more upward-swimming medusae exposed to an experimentally created stream of seawater that gently pushed them horizontally turned and swam down than did upward-swimming medusae not exposed to the seawater stream. Downward-swimming medusae continued to swim down when pushed horizontally. A stronger seawater stream that tumbled as well as pushed medusae horizontally was less effective. In a shallow area near the time of a low tide, most medusae were in the top metre of a 2 m water column whilst in an adjacent area where the water was 4–6 m deep, almost all medusae were below 1.5 m. These observations add to a growing body of evidence that the ecological distribution of A. labiata is influenced by their ability to respond adaptively to significant environmental stimuli.