Effects of copper on the coral-reef echinoid Echinometra mathaei

The effects of copper-enriched seawater on fertilization success, early cleavage, larval skeletal development, and survivorship of adults of the coral-reef echinoid Echinometra mathaei (de Blaiville) were tested. Fifty percent reduction of fertilization success and cleavage success to the 8-cell stage occurred in 0.18 and 0.42 mg added Cu⁺⁺/l, respectively. Adults had respective 48- and 96-h TL₅₀ values of 0.54 and 0.30 mg/l. Larval skeletal development was suppressed in 0.02 mg/l. The latter process appears to be very sensitive and may be the most suitable for assessing effects of stress on this species.Contribution No. 68, University of Guam Marine Laboratory.     

Effects of temperature on the mortality and growth of Hawaiian reef corals

Three common species of Hawaiian reef corals, Pocillopora damicornis (L.), Montipora verrucosa (Lamarck) and Fungia scutaria Lamarck, were grown in a temperature-regulated, continuous-flow sea water system. The skeletal growth optimum occurred near 26°C, coinciding with the natural summer ambient temperature in Hawaii, and was lowest at 21° to 22°C, representing Hawaiian winter ambient. Levels of approximately 32°C produced mortality within days. Prolonged exposure to temperatures of approximately 30°C eventually caused loss of photosynthetic pigment, increased mortality, and reduced calcification. Corals lived only 1 to 2 weeks at 18°C. The corals showed greater initial resistance at the lower lethal limit, but ultimately low temperature was more deleterious than high temperature. Results suggest that a decrease in the natural water temperature of Hawaiian reefs would be more harmful to corals than a temperature increase of the same magnitude.Contribution No. 504 of the Hawaii Institute of Marine Biology.     

Critical thermal maxima of two species of estuarine fish

Critical thermal maxima (CTM) were determined for winter flounder (Pseudopleuronectes americanus, Walbaum) and scup (Stenotomus chrysops, L.), acclimated to ambient water temperature or constant increments above ambient. The acclimation regimes simulated a natural environment by tracking the temperature fluctuations in Point Judith Pond, a small Rhode Island estuary. An elevation in CTM from 30.2° to 35.6°C was observed for scup as the mean acclimation temperature increased from 14.8° to 22.2°C. CTM for flounder increased from 26.4° to 32.4°C over an acclimation range of 4.2° to 23.0°C. The use of CTM studies for predicting the effects of heated effluents is discussed.     

Comparison of larval development and growth of the sea cucumberActinopyga echinites: Ovary-induced ova and DTT-induced ova

AdultActinopyga echinites (Jaeger) were collected from northern Taiwan in September 1989. Oocytes were induced to mature by bathing them in ovary juice (ovary-induced ova) or in 10^–2 M dithiothreitol (DTT-induced ova). The percentage of germinal vesicle breakdown (GVBD) increased from 0.4 to 6.4% in the former treatment and to 84% in the latter. After artificial fertilization, the embryos were cultured in seawater (35 S) at 25 to 28°C. Larvae were fed with the algaIsochysis aff.galbana at 10^4–5 cells/ml. Larvae from ovary-induced ova developed faster (18 d to the doliolaria stage) and grew to a larger size (1.13 mm length) than those from DTT-induced ova (20 d to the doliolaria stage and 0.62 mm in length). On the twelfth day, larvae from ovary-induced ova bear lipid spheres. The number of spheres is positively correlated with larval size. Lipid spheres may provide nutrient reserves for larvae during metamorphosis.     

Aspects of the biology of resting spores of Thalassiosira nordenskioeldii and Detonula confervacea

Large numbers of resting spores of Thalassiosira nordenskioeldii Cleve and Detonula confervacea (Cleve) Gran were produced when these species were grown at low levels of ammonia and nitrate. The production of resting spores by T. nordenskioeldii was inversely related to temperature. At 0° and 5°C between 68 and 96% of the total cells were resting spores, while at 15°C resting spores were not produced. Resting spores of both species would not survive 7 days in the dark at 20°C. At 0°, 5°, 10° and 15°C, the length of time that the resting spores of both T. nordenskioeldii and D. confervacea remained viable was inversely related to temperature. At 0°C, T. nordenskioeldii remained viable for 576 days. The data suggest that the production of resting spores by these two species does not aid them in the survival of unfavorably high temperatures such as are found in temperate estuaries during the summer. Rather, they appear to be an adaptation for the survival of long periods of darkness in polar regions.     

Heat tolerance,growth and regeneration in three North Sea bryozoans exposed to different constant temperatures

Three species of bryozoans—Membranipora membranacea (L.), Electra pilosa (L.) and Conopeum reticulum (L.) — are capable of acclimating to elevated temperatures, above the normal range experienced in nature, when exposed to a gradual increase in ambient temperature. Conspicuous differences in LD 50 values, as a consequence of acclimation, occur between representatives of the same species acclimated and grown at constant temperatures in the laboratory. The tolerance range of these species is influenced by their thermal history in the laboratory. While increased ambient temperatures accelerate growth rate, final colony size attained after prolonged exposure declines at higher temperatures. The size of zooecia attained is inversely proportional to the test temperature. Colonies of E. pilosa maintained at 22°C develop erect branches. Hence, it is probable that E. pilosa forma erecta is only a growth form of normally encrusting colonies of E. pilosa. Temperature affects rate of regeneration.     

Effect of temperature on the molting,growth and maturation of the antarctic krill Euphausia superba (Crustacea: Euphausiacea) under laboratory conditions

The effect of temperature on molting, growth, and maturation rates was studied on laboratory-maintained Euphausia superba. The length of intermolt periods (IMP's) was inversely proportional to temperature (20.10 d, SD=1.60, at 0.12°C; 16.87 d, SD=1.68, at 0.97°C; and 12.48 d, SD=0.90, at 4.48°C), and directly proportional to krill size at 0.12°C and 0.97°C. For individually maintained krill the maximum growth rate at 4.48°C (0.068 mm d^-1) was nearly twice that at 0.68°C (0.037 mm d^-1). There was no observable temperature effect on maturation rates. The maturation changes of juveniles at all temperatures indicated that more than two years are probably required to reach maturity. Mature males and females regressed to immature forms, suggesting that E. superba may reproduce in successive years. These results and previously reported field and laboratory data for E. superba and other euphausiid species suggest a 4+ year life span for this species.This work was supported by NSF grant DPP 76-23437     

Effect of temperature on the microdistribution of the isopod Sphaeroma rugicauda from a saltmarsh habitat

The saltmarsh isopod Sphaeroma rugicauda (Leach) is subjected to widespread diurnal and seasonal temperature fluctuations under natural conditions. Laboratory studies on its activity show that there is a relationship between behaviour activity and exposure temperature between 2.5° and 25°C. Although S. rugicauda has no complex metabolic adaptations, this isopod is able to maintain a rate of aerial oxygen consumption which is similar to that in water within the temperature range 5° to 25°C. The responses of S. rugicauda to changes in environmental temperature are discussed in relation to the seasonal microdistribution of the isopod in the salt-marsh habitat.     

Effects of seasonality and population density on the reproduction of the Indo-Pacific echinoid<Emphasis Type="Italic"> Echinometra mathaei</Emphasis> in Kenyan coral reef lagoons

Reproduction in the widely distributed tropical sea urchin Echinometra mathaei (de Blainville) was examined in three Kenyan reef lagoons that differed in substrate cover and E. mathaei population density. Histological examination of the gonads and gonad index measurements for 3 years showed a seasonal reproductive cycle with gametogenesis commencing in July, when temperature and light are at their lowest, and spawning commencing in December and peaking in February to May, when temperature and light reach their annual maxima. Monthly gonad indices correlated significantly with seawater temperature and light intensity. Male urchins had mature gametes for a longer period (8 months) than females (6 months), possibly an adaptive strategy that increases the probability of fertilization. Lunar periodicity was not observed, as male and female gonads were full of gametes on all days of the lunar cycle during the period of spawning. The peak in spawning activity coincides with the peak in phytoplankton abundance, which could ensure high food availability for the planktonic larvae. Gonad weights were significantly higher relative to urchin weight at the reef having the largest mean sizes and lowest population of urchins, indicating availability of food resources for growth and reproduction. E. mathaei at the reef with the highest density had the smallest urchins and high relative gonad sizes, indicative of a tradeoff between growth and reproduction when food is limited.Communicated by O. Kinne, Oldendorf/Luhe     

Slow developing demersal embryos and larvae of the antarctic sea star Odontaster validus

The early development of Odontaster validus at McMurdo Sound, Antarctica, is indirect and includes equal cleavage, a convoluted blastula, a free-swimming coeloblastula, a gastrula, and a feeding bipinnaria larva. Development differs from that of other asteroids in two respects: (1) The developmental rate is extremely slow; blastulae form nearly 2 days after fertilization, gastrulation begins after 7 days, and the bipinnaria develops in about 40 to 55 days. The slow developmental rate appears to be only partly related to the low environmental temperature (-1.5°C). (2) The embryos and larvae are largely demersal. Such behavior may be an adaptation to keep the larvae out of antarctic surface waters, as does brooding in many other polar echinoderms.     

Improved survival under heat stress in intertidal embryos (<Emphasis Type="Italic">Fucus</Emphasis> spp.) simultaneously exposed to hypersalinity and the effect of parental thermal history

Intertidal organisms exposed to thermal stress normally experience other stresses simultaneously, but how these combined stresses modify tolerance to heat, especially for embryos, is poorly understood. Tolerance of fucoid algal embryos to heat, with and without acclimation to a sublethal temperature and with simultaneous exposure to hypersaline media, was examined. Embryos of Fucus vesiculosus L. (mid-intertidal zone) were less tolerant than embryos of Fucus spiralis L. (upper intertidal zone); without acclimation and with a growth temperature of 14°C, about half of the embryos survived 3 h exposure to 33°C in F. vesiculosus and of 35°C in F. spiralis. Conditions experienced by parental thalli (4°C versus 14°C storage) significantly affected the heat tolerance of embryos grown for 24 h post-fertilization at 14°C in F. vesiculosus, a result that is important for biologists using fucoid algae as model systems. Acclimation to a sublethal temperature (29°C) or exposure to the LT₅₀ (33°C, F. vesiculosus; 35°C, F. spiralis) in 100 psu seawater (2850 mmol kg^–1 osmolality) resulted in 30–50% higher levels of embryonic survival. Higher levels of HSP60s were found in embryos exposed to 29–33°C than to 14°C; lower levels of HSP60s were present in embryos exposed to the LT₅₀ under hypersaline conditions than in normal seawater. Contemporaneous studies in 1995–1996 of substratum temperature and desiccation levels were made at Schoodic Point, Maine (USA) underneath F. spiralis and F. vesiculosus canopies and in Semibalanus balanoides patches. This study extends the bioindicator utility of heat-shock proteins in studies of intertidal organisms and demonstrates the importance of integrated stress responses in survival of a single stress factor (e.g. temperature).Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Response of gametophytes of Ecklonia radiata (Laminariales) to temperature in saturating light

Gametophytes of Ecklonia radiata (C.Ag.)J.Ag. from two New Zealand locations with different field temperature ranges were exposed to temperatures of 5° to 26°C in saturating light. Plants from Goat Island Bay (Lat. 36° 16S, Long. 174°48E) grew in 9.3° to 25°C and reproduced in 9.3° to 24°C. There was no growth at 8°C and plants died at 26°C. Plants from the cooler location, Houghton Bay (Lat. 41°20S, Long. 174°40E), grew from 8° to 24°C and reproduced up to 15°C but not at 21.5°C. The plants did not grow at 6°C and died at 26°C. The timing of the first cell division and subsequent growth rate were retarded close to the upper and lower tolerance limits. Reproduction was a broad optimum of roughly 12° to 20°C. Within this range, fertile female gametophytes grown at lower temperatures had fewer, larger cells and thus fewer potential ova than those grown at higher temperatures.     

Interacting pressure and temperature effects on enzymes of marine poikilotherms: Catalytic and regulatory properties of FDPase from deep and shallow-water fishes

At low temperature (3°C), and in the absence of substrate and cofactor, the enzyme, fructose diphosphatase (FDPase), extracted from liver of the benthic fishCoryphaenoides acrolepis, is reversibly inactivated by exposure to relatively low pressures (5,000 psi). At pressures of 20,000 psi at 3°C the native enzyme is irreversibly denatured. When the cofactor and the substrate are present, the enzyme is protected against pressure denaturation; hence, catalysis is insensitive to at least 10,000 psi at 3°C. Similarly, interactions between FDPase and its negative modulator adenosine monophosphate (AMP), are largely pressure insensitive. Pressure sensitivity of the native enzyme and of the catalytic process is much reduced at temperatures above about 9°C. The homologous enzyme from a surface fish,Pimelometopon pulchrum, is strikingly more sensitive to pressure, particularly at low temperatures.     

High-temperature tolerance of photosynthesis in the red alga Chondrus crispus

Chondrus crispus (Stackhouse) is a perennial red seaweed, common in intertidal and shallow sublittoral communities throughout the North Atlantic Ocean. In the intertidal zone, C. crispus may experience rapid temperature changes of 10 to 20C° during a single immerison-emerision cycle, and may be exposed to temperatures that exceed the thermal limits for long-term survival. C. crispus collected year-round at Long Cove Point, Chamberlain, Maine, USA, during 1989 and 1990, underwent phenotypic acclimation to growth temperature in the laboratory. This phenotypic acclimation enhanced its ability to withstand brief exposure to extreme temperature. Plants grown at summer seawater temperature (20°C) were able to maintain constant rates of lightsaturated photosynthesis at 30°C for 9 h. In contrast, light-saturated photosynthetic rates of plants grown at winter seawater temperature (5°C) declined rapidly following exposure to 30°C, reached 20 to 25% of initial values within 10 min, and then remained constant at this level for 9 h. The degree of inhibition of photosynthesis at 30°C was also dependent upon light intensity. Inhibition was greatest in plants exposed to 30°C in darkness or high light (600 mol photons m^-2s^-1) than in plants maintained under moderate light levels (70 to 100 mol photons m^-2s^-1). Photosynthesis of 20°C-acclimated plants was inhibited by exposure to 30°C in darkness or high light, but the degree of inhibition was less than that exhibited by 5°C-grown plants. Not only was light-saturated photosynthesis of 20°C plants less severely inhibited by exposure to 30°C than that of 5°C plants, but the former also recovered faster when they were returned to growth conditions. The mechanistic basis of this acclimation to growth temperature is not clear. Our results indicate that there were no differences between 5 and 20°C-grown plants in the thermal stability of respiration, electron transport associated with Photosystems I or II, Rubisco or energy transfer between the phycobilisomes and Photosystem II. Overall, our results suggest that phenotypic acclimation to seawater temperature allows plants to tolerate higher temperatures, and may play an important role in the success of C. crispus in the intertidal environment.     

Influence of high temperature and residual chlorine on marine phytoplankton

Marine phytoplankton forms are frequently exposed to sudden biological changes such as rapid rise in water temperature and chlorine content of their environment, resulting from the use of sea water for cooling purposes by electric generators. The direct influence of these effluents, i.e. inhibitory effects of high temperature and residual chlorine on growth and photosynthesis of Chlamydomonas sp. and Skeletonema costatum, were investigated experimentally. Chlamydomonas sp. and S. costatum exposed to high temperatures were affected in their growth from 43° and 35°C, respectively, by immersion of the respective cultures in a warm bath for 10 min. Treatment at high temperatures of 40 °C and 30° 35°C for 10 min, influenced their photosynthetic activities, which were completely inhibited immediately after 10 min exposure at 42° and 37 °C, respectively. S. costatum was killed by chlorine at a concentration of 1.5 2.3 ppm when exposed for exactly 5 or 10 min, while Chlamydomonas sp. was not irreversibly damaged even at 20 ppm chlorine or more with the same exposure period. These results lead to the conclusion that the high temperature of, and residual chlorine in, effuents from a power plant discharging into the open sea, should not cause great damage to marine phytoplankton in that area.     

Ecology of Echinometra mathaei (Echinoidea: Echinodermata) at Diani Beach,Kenya

Studies were carried out on the inner and outer coral reefs at Diani Beach on the Kenya coast to assess the distribution, density and behaviour of Echinometra mathaei (de Blainville). Transects 1 m wide were run on the two reefs in April, June and September, 1970. Test measurements on representative samples from the animal populations on both reefs were also taken. Direct observations on specimens of E. mathaci in selected rock pools on the outer reef were made to determine their movement, gregariousness, homing and feeding behaviour. Population density was higher on the inner reef furthest from the sea at low tide than on the outer reef. On the submerged inner coral reef at low tide, E. mathaei occurred mainly exposed on the seaweeds, but, on the exposed outer reef, its main niches were crevices in rock pools and under coral ledges. Sizefrequency distributions revealed that smaller individuals occurred on the inner reef and larger ones on the outer reef. The growth rate of E. mathaei was estimated from the positions of modal values, calculated from size-frequency distributions. No gregarious or homing behaviour was observed and, once settled in a suitable crevice, E. mathaei showed little movement.     

Interactive effects of light and temperature on sporophyte production in the giant kelp Macrocystis pyrifera

Laboratory experiments were conducted in 1984 to test for an interaction between irradiance and temperature in controlling sporophyte production in the giant kelp Macrocystis pyrifera. Gametophytes from plants in the San Onofre kelp forest were cultured under a combination of seven irradiance (2.9 to 30 E m^-2 s^-1) and ten temperature (11° to 20°C) levels. The minimum daily quantum dose for fertility of female gametophytes during the 42 d culture-period was 0.25 E m^-2 d^-1. The saturation quantum dose was approximately 0.60 E m^-2 d^-1. Temperatures between 11° and 20°C had little effect on the fertilityirradiance relationship, except at irradiations near the threshold and saturation levels. Cultures at 0.60 E m^-2 d^-1 had significantly lower fertility after 6 wk at 20°C than at the lower temperatures and there was a trend toward lower fertility at temperatures greater than 15°C in cultures at 0.25 E m^-2 d^-1. These differences were also reflected in the development time for female gametophytes. The 11°C cultures reached 50% fertility slightly faster and the 20°C cultures slower than cultures at intermediate temperatures.     

Effects of water-soluble oil fractions on metabolism,growth and carbon budget of the shrimp Crangon crangon

Juvenile shrimp, Crangon crangon L., were maintained in water-soluble crude oil fractions at 10°, 15° and 20°C. During chronic exposure to oil fractions, a reduction in respiration and growth rate occurred which was related to strength of the extract. Mortality increased with strength of oil fraction and was highest at 20°C. Calculation of carbon budgets indicated that the extract reduced net carbon turnover at each temperature. Physiological consequences resulting from exposure to the oil fractions are discussed.     

Mass mortality of Strongylocentrotus droebachiensis (Echinodermata: Echinoidea) off Nova Scotia,Canada

A mass mortality of Strongylocentrotus droebachiensis, attributed to disease, was monitored in an echinoiddominated barren ground at Eagle Head on the south-western coast of Nova Scotia, Canada, in 1982. Mortality was 70% in a shallow (3 m) nearshore area, resulting in a loss of echinoid biomass of 2 042 g fresh weight m^-2, and 6% in deeper (7 m, 10 m) offshore areas. Echinoid density, size and nutritional condition (gonad index) were highest in the nearshore area. Survivorship was higher in juveniles (<15 mm diameter) than in adults resulting in the formation of a bimodal size distribution in the nearshore area. Mortality began around early October, near the peak of the annual cycle of seawater temperature (15°C), and was arrested by early December (seawater temperature 7°C) when morbid echinoids appeared to recover. In laboratory experiments, time to morbidity of S. droebachiensis exposed to morbid conspecifics increased exponentially with decreasing temperature (20° to 8°C). There was no survival at 20° and 16°C, 20% survival at 12°C and 100% survival at 8°C after 60 d; suggesting a lower temperature limit (between 12° and 8°C) for possible transmission of a pathogenic agent. Morbid laboratory echinoids from experiments at 16°C, and recovering echinoids collected in the nearshore area in early December, showed 100 and 85% survival respectively at <=8°C, and 0 and 15% survival respectively at 16°C, after 30 d. Time to morbidity was not affected significantly by nutritional condition and was similar for juvenile and adult echinoids. Time to morbidity was greater in echinoids exposed to one or three morbid individuals continuously, or seven morbid individuals for 1 h, relative to higher levels of exposure (up to seven morbid individuals continuously). Recent mass mortalities in S. droebachiensis have occurred in years of record high sea surface temperatures. The extent of mortality is correlated with the magnitude and duration of temperatures above a lower limit.     

Effects of temperature on photosynthesis and respiration in hermatypic corals

Photosynthesis and respiration rates of the reef corals Pocillopora damicornis (Linn.), Montipora verrucosa (Lamarck), Porites compressa Dana and Fungia scutaria Lamarck were measured under controlled temperatures. Results indicate that coral metabolism is closely adapted to ambient temperature conditions. Tropical corals measured at Enewetak, Marshall Islands, showed greater primary production compared to maintenance requirements at elevated temperatures than did subtropical varieties of the same species in Hawaii. Photosynthesis: respiration (P:R) ratios were significantly and negatively related with temperature between 18° and 31°C for all Hawaiian corals, whereas at Enewetak this ratio generally showed a curvilinear relationship for this temperature range. Extrapolations of P:R regressions on temperatures to a value of 2.0 (estimated as a minimum required for long-term functional autotrophy) coincide for Hawaiian specimens with published upper lethal temperatures. Extrapolation of P:R regressions for Enewetak specimens at temperatures above 25°C suggests lethal temperatures for these corals to be 2 to 5 C° higher than for Hawaiian corals, in good agreement with recent experimental findings. Interspecific differences in P:R temperature regressions for Hawaiian corals correlating with upper lethal temperature tolerances are described.Contribution No. 505 of the Hawaii Institute of Marine Biology.