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 fertilization and early cleavage of some tropical echinoderms,with emphasis on Echinometra mathaei

Select temperatures, above normal, are shown to reduce success of fertilization and normal early cleavage in the laboratory for the echinoderms Acanthaster planci (L.), Culcita novaeguineae Muller and Troschel, Linckia laevigata (L.), Echinometra mathaei (de Blainville), and Diadema savignyi Michelin. The data indicate that cleavage is more sensitive to increased temperature than is fertilization. Upper tolerance limits for early cleavage in most of the species examined is near 34.0°C. The early developmental stages of A. planci were the most sensitive to elevated temperature, and those of E. mathaei, the least sensitive. Further experiments with E. mathaei showed that unfertilized ova were still viable, dividing normally when fertilized after 2 h exposure at 36.0°C. The ova were significantly less viable after 3 h. Early cleavage stages of E. mathaei were resistant to 36.0°C for exposure times of up to 40 min, but were inhibited beyond this period. It is suggested that the ability of E. mathaei to develop normally at 34.0°C (6C° above ambient temperature) and to withstand limited exposure to 36.0°C may account for the wide distribution of this species in habitats which are often subjected to broad temperature fluctuations, such as reef flats.Contribution No. 46 from the University of Guam Marine Laboratory.     

Comparing the effect of elevated pCO2 and temperature on the fertilization and early development of two species of oysters

This study compared the synergistic effects of elevated pCO₂ and temperature on the early life history stages of two ecologically and economically important oysters: the Sydney rock oyster, Saccostrea glomerata and the Pacific oyster, Crassostrea gigas. Gametes, embryos, larvae and spat were exposed to four pCO₂ (375, 600, 750, 1,000 μatm) and four temperature (18, 22, 26, 30°C) levels. At elevated pCO₂ and suboptimal temperatures, there was a reduction in the fertilization success of gametes, a reduction in the development of embryos and size of larvae and spat and an increase in abnormal morphology of larvae. These effects varied between species and fertilization treatments with S. glomerata having greater sensitivity than C. gigas. In the absence of adaptation, C. gigas may become the more dominant species along the south-eastern coast of Australia, recruiting into estuaries currently dominated by the native S. glomerata.     

Effects of ethynylestradiol and bisphenol A on the development of sea urchin embryos and juveniles

The effects of various concentrations of a synthetic estrogen, ethynylestradiol (EER), and an estrogenic compound, bisphenol A (BPA), on the development of two sea urchin species, Hemicentrotus pulcherrimus and Strongylocentrotus nudus, were examined. At concentrations of 2.5 μM or higher of EER the zygotes did not hatch; at 0.98–1.25 μM they developed but had abnormal morphology; and at concentrations lower than 1 μM there was no effect on embryogenesis. The dose dependency was the same for both species, but more embryos of S. nudus showed exogastrulation at 3–10 μM EER. The effect of BPA on early development was less remarkable than that of EER; most embryos developed normally even in the presence of 2.5 μM BPA. The feeding larvae progressed and finally metamorphosed into juveniles even at 0.1–3 μM EER. The chemicals had opposing effects on the growth of the juveniles. A low dose of EER (0.1–1 μM) promoted growth and the average diameter of the test was bigger than that of the control group; the same dose of BPA suppressed growth and the test was smaller than that of the control group. These results show that the sensitivity and response to endocrine disrupter chemicals changes markedly during the ontogeny of sea urchins. Physical and Chemical Impacts on Marine Organisms, a Bilateral Seminar Italy-Japan held in November 2004     

Limited effects of Antarctic ozone depletion on sea urchin development

The sea urchin, Sterechinus neumayeri, has a circumpolar distribution and is an abundant species in benthic communities of the Antarctic. Reproduction occurs during austral spring, when ozone concentrations over the past 25 years have been reduced by 50% or more, potentially exposing the planktonic embryos and larvae to elevated levels of UVB. During spring of 1996, cultures of S. neumayeri embryos incubated under ambient and partitioned sunlight (minus UVB) at static depths between 0 and 7 m were analyzed for DNA damage [cyclobutane pyrimidine dimers (CPDs)] and morphological abnormalities. At 0-m and 1-m depths, nearly 100% of embryos developed abnormally, even under UVB-shielded conditions where little or no DNA damage accumulated. At depths >3 m, reduced or no abnormality was evident and DNA damage was negligible. Although UVB contributed to 0–65% of solar-induced abnormalities, the mean contribution was 11±17% and UVB was not primarily responsible for observed defects in urchin development. Moreover, developmental responses were not linearly related to ambient UVB gradients as might be expected, but are better characterized relative to threshold levels of total UVB exposure. Accumulated exposures of 25 kJ m^–2 ambient UVB caused minimal DNA damage and allowed normal embryological development to proceed. Higher UVB exposures (especially 80 kJ m^–2) precluded normal development. An ancillary threshold limit of 17 CPDs mb^–1 has been identified as the level of DNA damage that proscribes abnormal development. While higher wavelengths of UVA and visible light are not affected by ozone concentration and do not initiate significant CPD DNA damage, they did interfere significantly with the embryological development of S. neumayeri. It is concluded that exposure to increased UVB during recent Antarctic ozone-depletion cycles probably has only a small degree of impact relative to the magnitude of other solar effects on the developmental success of Sterechinus embryos, or compared to spawning seasons before ozone depletion (i.e., years prior to 1978).Communicated by P.W. Sammarco, Chauvin     

Effects of sea urchin disease on coastal marine ecosystems

Outbreaks of disease in herbivorous sea urchins have led to ecosystem phase shifts from urchin barrens to kelp beds (forests) on temperate rocky reefs, and from coral to macroalgal-dominated reefs in the tropics. We analyzed temporal patterns in epizootics that cause mass mortality of sea urchins, and consequent phase shifts, based on published records over a 42-year period (1970–2012). We found no evidence for a general increase in disease outbreaks among seven species of ecologically important and intensively studied sea urchins. Periodic waves of recurrent amoebic disease of Strongylocentrotus droebachiensis in Nova Scotia coincide with periods when the system was in a barrens state and appear to have increased in frequency. In contrast, following a major epizootic that decimated Diadema antillarum throughout the Caribbean in 1983, subsequent outbreaks of disease were highly localized and none have been reported since 1991. Epizootics of Strongylocentrotus in the NW Atlantic and NE Pacific, and Paracentrotus and Diadema in the eastern Atlantic, have been linked to climate change and overfishing of sea urchin predators. The spatial extent of recurrent disease outbreaks in these species, and the frequency of phase shifts associated with these epizootics, has decreased over time due to the expansion of the macroalgal state and its stabilization through positive feedback mechanisms. Longitudinal studies to monitor disease outbreaks in sea urchin populations and improved techniques to identify causative agents are needed to assess changes in the frequency and extent of epizootics, which can profoundly affect the structure and functioning of coastal marine ecosystems.     

Structural and functional vulnerability to elevated pCO2 in marine benthic communities

The effect of elevated pCO₂/low pH on marine invertebrate benthic biodiversity, community structure and selected functional responses which underpin ecosystem services (such as community production and calcification) was tested in a medium-term (30 days) mesocosm experiment in June 2010. Standardised intertidal macrobenthic communities, collected (50.3567°N, 4.1277°W) using artificial substrate units (ASUs), were exposed to one of seven pH treatments (8.05, 7.8. 7.6, 7.4, 7.2, 6.8 and 6.0). Community net calcification/dissolution rates, as well as changes in biomass, community structure and diversity, were measured at the end of the experimental period. Communities showed significant changes in structure and reduced diversity in response to reduced pH: shifting from a community dominated by calcareous organisms to one dominated by non-calcareous organisms around either pH 7.2 (number of individuals and species) or pH 7.8 (biomass). These results were supported by a reduced total weight of CaCO₃ structures in all major taxa at lowered pH and a switch from net calcification to net dissolution around pH 7.4 (Ω_calc = 0.78, Ω_ara = 0.5). Overall community soft tissue biomass did not change with pH and high mortality was observed only at pH 6.0, although molluscs and arthropods showed significant decreases in soft tissue. This study supports and refines previous findings on how elevated pCO₂ can induce changes in marine biodiversity, underlined by differential vulnerability of different phyla. In addition, it shows significant elevated pCO₂-/low pH-dependent changes in fundamental community functional responses underpinning changes in ecosystem services.     

大气CO2体积分数升高环境温度与土壤水分对农田土壤呼吸的影响

植物-土壤生态系统土壤呼吸与温度、水分环境因子的关系对评价目前大气CO2浓度持续升高背景下陆地生态系统土壤碳库的变化趋势具有重要意义.依托FACE(free air carbon dioxide enrichment)技术平台,利用阻断根法,采用LI-6400红外气体分析仪(IRGA)-田间原位测定的方法,研究了大气CO2体积分数升高对稻(Oryza sativa L.)/麦(Triticum aestivum L.)轮作制中麦田的土壤呼吸、基础土壤呼吸和呼吸主要影响因子,分析了大气CO2体积分数升高后温度与水分对土壤呼吸的影响.结果表明,在整个测定期间,土壤呼吸与基础土壤呼吸速率呈明显的季节变化,与气温和土壤温度季节变化趋势基本一致,呼吸速率与温度具有显著的相关性,是影响土壤呼吸的控制性因素;呼吸速率与土壤含水量无显著的相关性,土壤水分是研究区麦田土壤CO2排放的非限制性因素,且温度与土壤含水量间的交互效应对土壤呼吸的影响不显著.基础土壤呼吸比作物下的土壤呼吸更易受温度影响,土壤温度比气温能更好地解释土壤CO2排放的季节性变化.而CO2体积分数增加降低了温度与呼吸速率间的相关系数和Q10,表明温度对土壤CO2排放的影响程度下降.但高CO2体积分数环境中植物-土壤生态系统的土壤呼吸对温度增加敏感性的降低,有利于减缓土壤碳分解损失的速度.结果有助于评价未来高CO2体积分数气候变暖背景下植物-土壤系统下的农田生态系统土壤碳的固定潜力.     

Effect of increasing sea water pCO2 on the northern Atlantic krill species Nyctiphanes couchii

Surprisingly little is known about potential effects of ocean acidification on krill of the Northern Hemisphere as ecologically very important food web component. Sub-adult individuals of the northern Atlantic krill species Nyctiphanes couchii (caught at Austevoll near Bergen, Norway, in January 2013) were exposed in the laboratory to four different levels of pCO₂ (430, 800, 1,100, and 1,700 µatm) for 5 weeks in order to assess potential changes in a set of biological response variables. Survival decreased and the frequency of moulting-related deaths increased with increasing pCO₂. Survival was considerably reduced at relatively high pCO₂ of 1,700 µatm and tended to be negatively affected at 1,100 µatm pCO₂. However, the experimental results show no significant effects of pCO₂ on inter-moult period and growth at pCO₂ levels below 1,100 µatm. No differences in length measurements of the carapace and uropod were observed across pCO₂ levels, indicating no effect of changing carbonate chemistry on the morphology of those calciferous parts of the exoskeleton. The results suggest that sub-adult N. couchii may not suffer dramatically from predicted near-future changes in pCO₂. However, potential detrimental effects on the moulting process and associated higher mortality at 1,100 µatm pCO₂ cannot be excluded. Further experiments are needed in order to investigate whether early life stages of N. couchii show a different sensitivity to elevated sea water pCO₂ and whether those results are transferable to other krill species of the Northern Hemisphere.     

The effect of seasonality on oxidative metabolism in the sea urchin Loxechinus albus

The objective of the present study was to investigate seasonal variations in the oxidative metabolism of the sea urchin Loxechinus albus gonads. The reported spawning period for this species is from September to November. Lipid radical content showed non-significant changes upon the seasons. Ascorbyl radical content and the content of α-tocopherol were lower in samples collected in spring and summer as compared to the values in winter-collected animals. Ascorbate content decreased in samples collected in fall as compared to those collected in winter. For the lipophilic compartment, the lipid radical content/α-tocopherol content ratio is an indicator of oxidative stress. This index increased significantly in tissues during spawning as compared to the values in samples collected during winter. The ascorbyl content/ascorbate content ratio is an indicator of oxidative stress for the hydrophilic milieu. A significant decrease by 66% was determined in tissues from gonads of animals collected in summer as compared to values in animals collected in winter. The data reported here suggest a different profile of response against oxidative stress at the lipophilic and hydrophilic milieus in L. albus gonads.     

Cuttlebone calcification increases during exposure to elevated seawater pCO2 in the cephalopod Sepia officinalis

Changes in seawater carbonate chemistry that accompany ongoing ocean acidification have been found to affect calcification processes in many marine invertebrates. In contrast to the response of most invertebrates, calcification rates increase in the cephalopod Sepia officinalis during long-term exposure to elevated seawater pCO₂. The present trial investigated structural changes in the cuttlebones of S. officinalis calcified during 6 weeks of exposure to 615 Pa CO₂. Cuttlebone mass increased sevenfold over the course of the growth trail, reaching a mean value of 0.71 ± 0.15 g. Depending on cuttlefish size (mantle lengths 44–56 mm), cuttlebones of CO₂-incubated individuals accreted 22–55% more CaCO₃ compared to controls at 64 Pa CO₂. However, the height of the CO₂-exposed cuttlebones was reduced. A decrease in spacing of the cuttlebone lamellae, from 384 ± 26 to 195 ± 38 μm, accounted for the height reduction The greater CaCO₃ content of the CO₂-incubated cuttlebones can be attributed to an increase in thickness of the lamellar and pillar walls. Particularly, pillar thickness increased from 2.6 ± 0.6 to 4.9 ± 2.2 μm. Interestingly, the incorporation of non-acid-soluble organic matrix (chitin) in the cuttlebones of CO₂-exposed individuals was reduced by 30% on average. The apparent robustness of calcification processes in S. officinalis, and other powerful ion regulators such as decapod cructaceans, during exposure to elevated pCO₂ is predicated to be closely connected to the increased extracellular [HCO₃ ⁻] maintained by these organisms to compensate extracellular pH. The potential negative impact of increased calcification in the cuttlebone of S. officinalis is discussed with regard to its function as a lightweight and highly porous buoyancy regulation device. Further studies working with lower seawater pCO₂ values are necessary to evaluate if the observed phenomenon is of ecological relevance.     

Tolerance of juvenile barnacles (Amphibalanus improvisus) to warming and elevated pCO2

We investigated the impacts of warming and elevated pCO₂ on newly settled Amphibalanus improvisus from Kiel Fjord, an estuarine ecosystem characterized by significant natural pCO₂ variability. In two experiments, juvenile barnacles were maintained at two temperature and three pCO₂ levels (20/24 °C, 700–2,140 μatm) for 8 weeks in a batch culture and at four pCO₂ levels (20 °C, 620–2,870 μatm) for 12 weeks in a water flow-through system. Warming as well as elevated pCO₂ hardly affected growth or the condition index of barnacles, although some factor combinations led to temporal significances in enhanced or reduced growth with an increase in pCO₂. While warming increased the shell strength of A. improvisus individuals, elevated pCO₂ had only weak effects. We demonstrate a strong tolerance of juvenile A. improvisus to mean acidification levels of about 1,000 μatm pCO₂ as is already naturally experienced by the investigated barnacle population.     

Effects of recruitment on genetic patchiness in the urchinEchinometra mathaei in Western Australia

Enzyme polymorphisms in the sea urchinEchinometra mathaei were examined to test the relative influences of population turnover and patchiness in recruitment on genetic heterogeneity. We found that the total variance in allelic frequency among three populations separated by approximately 4 km at Rottnest Island, Western Australia (collected in February 1985) is as large as that among five additional samples collected over a distance of 1 300 km along the Western Australian coast in August 1987. This suggests that the forces causing genetic differentiation act on a local scale and occur in a single generation. A comparison of sites with different histories of recruitment indicates that the observed genetic differences among age groups are the result of prerecruitment effects, and that differences among sites reflect their individual histories of recruitment.     

Brooded coral larvae differ in their response to high temperature and elevated pCO2 depending on the day of release

To evaluate the effects of temperature and pCO₂ on coral larvae, brooded larvae of Pocillopora damicornis from Nanwan Bay, Taiwan (21°56.179′N, 120°44.85′E), were exposed to ambient (419–470 μatm) and high (604–742 μatm) pCO₂ at ~25 and ~29 °C in two experiments conducted in March 2010 and March 2012. Larvae were sampled from four consecutive lunar days (LD) synchronized with spawning following the new moon, incubated in treatments for 24 h, and measured for respiration, maximum photochemical efficiency of PSII (F _v/F _m), and mortality. The most striking outcome was a strong effect of time (i.e., LD) on larvae performance: respiration was affected by an LD × temperature interaction in 2010 and 2012, as well as an LD × pCO₂ × temperature interaction in 2012; F _v/F _m was affected by LD in 2010 (but not 2012); and mortality was affected by an LD × pCO₂ interaction in 2010, and an LD × temperature interaction in 2012. There were no main effects of pCO₂ in 2010, but in 2012, high pCO₂ depressed metabolic rate and reduced mortality. Therefore, differences in larval performance depended on day of release and resulted in varying susceptibility to future predicted environmental conditions. These results underscore the importance of considering larval brood variation across days when designing experiments. Subtle differences in experimental outcomes between years suggest that transgenerational plasticity in combination with unique histories of exposure to physical conditions can modulate the response of brooded coral larvae to climate change and ocean acidification.     

Effects of food ration and feeding regime on growth and reproduction of the sea urchin Strongylocentrotus droebachiensis

To determine the effects food ration and feeding regime on growth and reproduction of Strongylocentrotus droebachiensis (Müller), sea urchins in laboratory aquaria were fed kelp (Laminaria longicruris) supplied at either a high (H, ad libidum daily) or a low (L, ad libidum 1 d wk⁻¹) ration in two successive 12-wk intervals during the reproductive period. After 24 wk, urchins fed the high ration continuously (HH) or for the last 12 wk only (LH) had a significantly greater mean gonad index [(gonad weight/total body weight) × 100] and body weight than urchins fed the low ration continuously (LL) or for the last 12 wk only (HL). Urchins in the HL treatment had a significantly greater gonad index than those in the LL treatment; there was no significant difference in gonad index between the LH and HH treatments. Females had a greater gonad index than males in the low ration (LL and HL) treatments at the end of the experiment; there was no significant difference between sexes in the high ration (LH, HH) treatments. Gametogenesis proceeded to maturation in all treatments and some individuals spawned at the end of the experiment. Females in the high ration (HH and LH) treatments had a greater proportion of nutritive phagocytes in their ovaries than females in the low ration treatments, but there was no effect of feeding treatment on oocyte or ovum size. Feeding treatment had no effect on the relative abundance of nutritive phagocytes in the testes, although the proportion of spermatocytes was higher (and that of spermatozoa lower) in the high ration than in the low ration treatments. Urchins in the high ration treatments had a lower mean jaw height index [(jaw height/test diameter) × 100] and greater mean test diameter than those in the low ration treatments at the end of the experiment, although these differences were not statistically significant. Feeding rate on kelp at the end of the experiment was significantly greater for urchins in the low ration than in the high ration treatments. Our experimental results show that even relatively low rations of kelp support somatic and gonadal growth in S. droebachiensis. Increasing the supply of kelp, particularly during the period of active gametogenesis, results in maximal rates of growth and reproduction. These results suggest that populations of S. droebachiensis in barrens may derive a substantial proportion of their nutrition from drift kelp, which may contribute to their persistence in these habitats. They also explain the large body size, high reproductive effort and fecundity of urchins grazing on kelp beds. These findings have important implications for understanding the dynamics of natural populations of S. droebachiensis and for development of effective aquacultural practices. Received: 17 February 1997 / Accepted: 5 March 1997     

Effects of food type and ration on reproductive maturation and growth of the sea urchin Strongylocentrotus droebachiensis

We investigated the effects of food quality and quantity on reproductive maturation and growth of juveniles of Strongylocentrotus droebachiensis (Müller) in a 22 month laboratory experiment in which we fed sea urchins four diets: (1) kelp (Laminaria spp.) for 6 d wk⁻¹ and mussel (Mytilus spp.) flesh for 1 d wk⁻¹ (KM); (2) kelp for 7 d wk⁻¹ (high ration, KH); (3) kelp for 1 d wk⁻¹ (low ration, KL) and (4) no food other than encrusting coralline algae (NF). At their first and second opportunity for reproduction, all sea urchins in the KM and KH treatments, and most in the KL treatment were reproductively mature, whereas all sea urchins in the NF treatment remained immature. Gonad index differed significantly among all fed treatments at first and second reproduction, and was highest in the KM and lowest in the KL treatment. Gonad index was similar in both sexes at first reproduction, but it was higher in females than in males at second reproduction. Diet had little or no effect on the relative abundance of spermatocytes, spermatozoa, or nutritive phagocytes in testes at first and second reproduction. In ovaries, nutritive phagocytes were significantly more abundant in females in the KM and KH treatments than in the KL treatment at first reproduction, and significantly more abundant in unfed (NF) than fed (KM, KH, KL) females at second reproduction. Mean oocyte size was similar in all fed females at first reproduction, but significantly larger in fed than unfed females at second reproduction. Mean ovum size was similar in all fed females in both reproductive periods. Increase in test diameter was greatest in the KM treatment and smallest in the KL treatment; sea urchins in the NF treatment decreased slightly in size. Survival was 95 to 100% in all fed sea urchins but significantly lower in unfed ones. The feeding rate on kelp was significantly greater in the KL than the KM and KH treatments. In the KM treatment, the feeding rate on kelp increased significantly over a 6 d period after mussel flesh was provided. Our results demonstrate that a diet of high food quality and quantity accelerates reproductive maturation and growth rate, and enhances gonad production and survival in juvenile and young adult S. droebachiensis. These findings contribute to our understanding of the reproductive ecology of S. droebachiensis in habitats with differing food supplies (e.g., kelp beds and barrens). Our results also can be used to improve aquacultural practices for sea urchins. Received: 3 June 1998 / Accepted: 2 February 1999     

Effects of predators on sea urchin density and habitat use in a southern California kelp forest

Grazing sea urchins can reduce kelp abundance and therefore strongly affect kelp forest community structure. Despite the ecological importance of sea urchins, direct field studies on the role that urchin predators play in shaping urchin populations are rare for southern California. We conducted surveys and manipulative experiments within kelp forests near San Diego, CA, (32–51′28″N, 117–16′00″W) from 2006 to 2009 to determine whether predators such as sheephead (Semicossyphus pulcher) and spiny lobsters (Panulirus interruptus) may be linked to purple urchin (Strongylocentrotus purpuratus) and red urchin (Strongylocentrotus franciscanus) distribution and habitat use, as well as purple urchin density-dependent mortality. Purple urchins were less dense and more cryptic inside a local marine protected area (MPA) that contained high predator abundance than in nearby heavily fished areas, whereas red urchins rarely were found outside the MPA. Urchin proportional mortality was inversely density dependent during the day when sheephead were active, despite fish aggregations in plots of high urchin density, but was density independent during the night when lobsters were active. Urchin mortality was reduced under understory algal cover during the day, but not during the night. Examining whether urchin mortality from predation is density dependent and how habitat complexity influences this relationship is imperative because behavioral changes and increases in urchin populations can have vast ecological and economic consequences in kelp forest communities.