Sea Urchin Evechinus Chloroticus Research Articles

Emergence of the subtropical sea urchin Centrostephanus rodgersii as a threat to kelp forest ecosystems in northern New Zealand

Marine protected areas have long been proposed as a key tool to restore lost food web interactions and increase the resilience of ecosystems to climate change impacts. However, a changing climate can result in the arrival of new species or differentially affect native species, which can alter ecosystem dynamics and make it difficult to predict how ecosystems will respond to protection. The long-spined sea urchin Centrostephanus rodgersii is a well-known range extender with large impacts on kelp forest ecosystems, yet its response to warming and long-term marine protection has not been examined within its native range. We examine long-term trends in C. rodgersii and the endemic sea urchin Evechinus chloroticus following no-take protection within the Poor Knights Islands Marine Reserve, in northeastern Aotearoa New Zealand, from 1999-2022, and compare with population trends at an unprotected island group. Within the marine reserve, E. chloroticus decreased in density, became more cryptic, and urchin barrens associated with this species largely disappeared, whereas in fished areas, populations and extent of barrens remained stable. This differing response between the reserve and fished location is consistent with a top-down effect and greater abundance of predatory fish in the reserve. In contrast, the subtropical sea urchin C. rodgersii increased in abundance by 9.3 times in the Poor Knights Island Marine Reserve and 4.3 times at the fished location, with areas of urchin barrens associated with this species developing at both locations. This increase coincides with substantial warming over the monitoring period (0.25°C decade-1) and low numbers of key predators (rock lobster) at both reserve and fished locations. This highlights the emerging threat of C. rodgersii to rocky reefs in the region and how marine protection alone may not increase resilience to this threat. This suggests multifaceted management approaches are needed to mitigate the impacts of emerging pest species and increase the resilience of temperate reef ecosystems in a warming climate.

Ocean acidification impacts sperm swimming performance and pHi in the New Zealand sea urchin Evechinus chloroticus.

In sea urchins, spermatozoa are stored in the gonads in hypercapnic conditions (pH<7.0). During spawning, sperm are diluted in seawater of pH>8.0, and there is an alkalinization of the sperm's internal pH (pHi) through the release of CO2 and H+. Previous research has shown that when pHi is above 7.2-7.3, the dynein ATPase flagellar motors are activated, and the sperm become motile. It has been hypothesized that ocean acidification (OA), which decreases the pH of seawater, may have a narcotic effect on sea urchin sperm by impairing the ability to regulate pHi, resulting in decreased motility and swimming speed. Here, we used data collected from the same individuals to test the relationship between pHi and sperm motility/performance in the New Zealand sea urchin Evechinus chloroticus under near-future (2100) and far-future (2150) atmospheric PCO2conditions (RCP 8.5: pH 7.77, 7.51). Decreasing seawater pH significantly negatively impacted the proportion of motile sperm, and four of the six computer-assisted sperm analysis (CASA) sperm performance measures. In control conditions, sperm had an activated pHi of 7.52. Evechinus chloroticus sperm could not defend pHi in future OA conditions; there was a stepped decrease in the pHi at pH 7.77, with no significant difference in mean pHi between pH 7.77 and 7.51. Paired measurements in the same males showed a positive relationship between pHi and sperm motility, but with a significant difference in the response between males. Differences in motility and sperm performance in OA conditions may impact fertilization success in a future ocean.

Effect of acclimation on thermal limits and hsp70 gene expression of the New Zealand sea urchin Evechinus chloroticus

Seawater temperature is projected to increase globally due to climate change, affecting physiological responses, fitness and survival of marine organisms. Thermal tolerance studies are critical to determine the ability of animals to adapt to future environmental conditions. In this study, we aimed to determine if the thermal limits of the New Zealand Evechinus chloroticus would shift with animal's thermal history. We tested the effect of six thermal regimes on the righting ability, temperature of loss of righting (TLOR), median lethal temperature (LT50), lethal temperature (LT) and the gene expression of the heat shock protein 70 (hsp70) of the New Zealand sea urchin E. chloroticus when exposed to a thermal shock of 1 °C day−1 (duration of 7–16 days depending on the treatment). Treatments consisted of laboratory acclimation for one and four weeks to 18 °C and 24 °C (mean winter (15 °C) and summer temperature (21 °C) + 3 °C of warming, respectively), compared to non-acclimated sea urchins collected during winter (14.6 °C) and summer seasons (20.4 °C). Thermal history did not have a significant effect on the righting ability of E. chloroticus (TLOR ranged between 28 and 29 °C for all treatments) and LT50 (ranged between 29 and 30 °C for all treatments). However, LT of E. chloroticus collected during winter season was significantly lower than animals acclimated for one week at 18 °C. Maximum expression of hsp70 mRNA (Tmax) was observed at around 27–28 °C regardless of treatment; however, relative hsp70 mRNA levels were significantly higher in animals acclimated for four weeks at 24 °C. Despite proving to be a thermotolerant species with LTs around 30 °C, E. chloroticus was unable to increase thermal tolerance and Tmax when acclimated to high temperatures, suggesting that E. chloroticus may have a limited adaptive capacity to modify its phenotype; however, evolutionary adaptations may allow E. chloroticus to adapt to future ocean temperatures.

PHNQ from Evechinus chloroticus Sea Urchin Supplemented with Calcium Promotes Mineralization in Saos-2 Human Bone Cell Line.

Polyhydroxylated naphthoquinones (PHNQs), known as spinochromes that can be extracted from sea urchins, are bioactive compounds reported to have medicinal properties and antioxidant activity. The MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay showed that pure echinochrome A exhibited a cytotoxic effect on Saos-2 cells in a dose-dependent manner within the test concentration range (15.625–65.5 µg/mL). The PHNQ extract from New Zealand sea urchin Evechinus chloroticus did not induce any cytotoxicity within the same concentration range after 21 days of incubation. Adding calcium chloride (CaCl2) with echinochrome A increased the number of viable cells, but when CaCl2 was added with the PHNQs, cell viability decreased. The effect of PHNQs extracted on mineralized nodule formation in Saos-2 cells was investigated using xylenol orange and von Kossa staining methods. Echinochrome A decreased the mineralized nodule formation significantly (p < 0.05), while nodule formation was not affected in the PHNQ treatment group. A significant (p < 0.05) increase in mineralization was observed in the presence of PHNQs (62.5 µg/mL) supplemented with 1.5 mM CaCl2. In conclusion, the results indicate that PHNQs have the potential to improve the formation of bone mineral phase in vitro, and future research in an animal model is warranted.

Injured conspecifics as an alarm cue for the sea urchin Evechinus chloroticus

Predator mediation of sea urchin grazing pressure may occur via lethal removal of individual sea urchins or non-lethal modification of sea urchin behaviour. Several studies have shown that predation-related cues can affect sea urchin movement and grazing rates, but generalisations about the types of cues that prompt responses and the magnitude of those responses will require further research on a wider variety of species. We examined the effects of potential alarm cues on behaviour of the habitat-forming sea urchin Evechinus chloroticus (Echinometridae) on fished rocky reefs in northeastern New Zealand, where predators are uncommon and the sea urchins form barrens. Exposed E. chloroticus (i.e. those not in crevices) rapidly fled from injured conspecifics within a 1 m radius of the cue, but showed no apparent reaction to injured sea urchins belonging to another family (Centrostephanus rodgersii, Diadematidae), diced pilchards or the disturbance caused by fish attracted to the cues. Densities of exposed sea urchins in an area containing injured conspecifics did not return to control values for at least 20 h, while cryptic individuals remained crevice-bound when injured conspecifics were nearby. Injured conspecifics thus provide a strong, albeit localised, cue for E. chloroticus. By restricting sea urchins to crevices where they have a reduced impact on living kelp, this non-consumptive effect may complement the lethal effects of predation in marine reserves where populations of predators such as rock lobsters and large fish are allowed to recover from overharvesting by humans, thereby reinforcing the trophic cascade initiated by those predators.

Sea urchin larvae show resilience to ocean acidification at the time of settlement and metamorphosis

Extensive research has shown that the early life stages of marine organisms are sensitive to ocean acidification (OA). Less is known, however, on whether larval settlement and metamorphosis may be affected, or by which mechanisms. These are key processes in the life cycle of most marine benthic organisms, since they mark the transition between the free swimming larval stage to benthic life. We investigated whether OA could affect the larval settlement success of the sea urchin Evechinus chloroticus, a key coastal species with ecological, economic and cultural importance in New Zealand. We performed four settlement experiments to test whether reduced seawater pH (ranging from 8.1 to 7.0, at an interval of ~0.2 pH units) alters larval settlement and metamorphosis success. Our results show that settlement success was not significantly reduced when the larvae were exposed to a range of reduced seawater pH treatments (8.1–7.0) at time of settlement (on direct effects). Similarly, when presented with crustose coralline algae (CCA) pre-conditioned in seawater pH of either pH 8.1 or 7.7 for 28 days, larval settlement success remained unaltered (on indirect effects). We conclude that competent larvae in this species are resilient to OA at time of settlement. Further research on a range of taxa that vary in settlement selectivity and behaviour is needed in order to fully understand the effects of OA on the life cycle of marine invertebrates and the consequences it might have for future coastal marine ecosystems.

Description and ecophysiology of a new species of Syndesmis Silliman, 1881 (Rhabdocoela: Umagillidae) from the sea urchin Evechinus chloroticus (Valenciennes, 1846) Mortensen, 1943 in New Zealand.

A new rhabdocoel of the genus Syndesmis Silliman, 1881 (Umagillidae) is described from the intestine of the New Zealand sea urchin Evechinus chloroticus (Valenciennes, 1846) Mortensen, 1943a. This new species, Syndesmis kurakaikina n. sp., is morphologically distinct and can easily be recognised by its very long (±1 mm) stylet and its bright-red colour. In addition to providing a formal description, we present some observations on reproduction and life history of this new species. Fecundity is comparable to that of other umagillids and the rate of egg production and development increases with temperature. Hatching in this species is induced by intestinal fluids of its host. Relevant to global warming, we assessed the effect of temperature on survival, fecundity, and development. The tests indicate that Syndesmis kurakaikina n. sp. is tolerant of a wide range of temperatures (11–25 °C) and that its temperature optimum lies between 18.0 and 21.5 °C. Egg viability is, however, significantly compromised at the higher end of this temperature range, with expelled egg capsules often being deformed and showing increasingly lower rates of hatching. Given this, a rise in global temperature might increase the risk of Syndesmis kurakaikina n. sp. infecting new hosts and would possibly facilitate the spread of these endosymbionts.

Low salinity and sediment stress on sea urchin Evechinus chloroticus larvae has latent effects on juvenile performance

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 619:85-96 (2019) - DOI: https://doi.org/10.3354/meps12951 Low salinity and sediment stress on sea urchin Evechinus chloroticus larvae has latent effects on juvenile performance Andrea Glockner-Fagetti*, Nicole E. Phillips School of Biological Sciences, Victoria University of Wellington, Wellington, 6012, New Zealand *Corresponding author: andglockner@gmail.com ABSTRACT: Coastal areas are affected by freshwater runoff that carries terrigenous sediments and reduces salinity, both of which can have deleterious effects on early life stages of marine organisms. The aim of this study was to experimentally assess the combined stress of low salinity and suspended or deposited sediments on larval and post-larval development of the sea urchin Evechinus chloroticus. Larvae were exposed to low salinity (28, 32 ppt) and suspended sediments (40, 80 mg l-1), in a fully factorial design, for 4 d, then returned to control conditions (36 ppt, 0 mg l-1). Four weeks later, competent larvae from every treatment were placed in bowls under control conditions to allow them to settle. To assess additional effects of deposited sediments on settlement, the bottoms of half of the bowls were covered with fine sediments. Seven days after fertilisation, larval development was reduced in the lowest salinity and suspended sediment treatments, but these differences were no longer visible by Day 21. Larval survival was not affected by the treatments. However, settlement success and juvenile development were reduced both by larval exposure to the lowest salinity and in the presence of deposited sediments. At 28 d post-settlement, there were no surviving juveniles that had been exposed either to the lowest salinity or to the highest level of suspended sediment early in larval life. Our findings suggest that even short exposure to runoff during early development can have strong consequences for later larval settlement and juvenile performance, which could compromise recruitment to adult populations. KEY WORDS: Latent effects · Multiple stressors · Runoff · Larval development · Settlement · Evechinus chloroticus Full text in pdf format PreviousNextCite this article as: Glockner-Fagetti A, Phillips NE (2019) Low salinity and sediment stress on sea urchin Evechinus chloroticus larvae has latent effects on juvenile performance. Mar Ecol Prog Ser 619:85-96. https://doi.org/10.3354/meps12951 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 619. Online publication date: June 04, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Extraction, structural characterization and stability of polyhydroxylated naphthoquinones from shell and spine of New Zealand sea urchin (Evechinus chloroticus)

The extraction of polyhydroxylated naphthoquinone (PHNQ) pigments from the shell and spines of the New Zealand sea urchin Evechinus chloroticus was evaluated using six different macroporous resins as an alternative to using organic solvent extraction alone. Four of the resins evaluated in this study (D4006, D4020, D101 and NKA-9) provided the best extraction of PHNQ pigments in terms of the overall adsorption and desorption of E. chloroticus PHNQ pigments from the resins. Organic solvents alone had a higher yield of PHNQs than the resins. The PHNQ composition was characterised by high-performance liquid chromatography (HPLC) with diode‐array detection and mass spectrometry. Five PHNQ compounds (spinochromes E, B, C, A and echinochrome A), and three aminated PHNQ compounds (spinamine E, echinamines A and B) were identified. The pigments were found to be prone to degradation on exposure to light, with the aminated PHNQ pigments being the least stable.

Predators indirectly induce stronger prey through a trophic cascade.

Many prey species induce defences in direct response to predation cues. However, prey defences could also be enhanced by predators indirectly via mechanisms that increase resource availability to prey, e.g. trophic cascades. We evaluated the relative impacts of these direct and indirect effects on the mechanical strength of the New Zealand sea urchin Evechinus chloroticus We measured crush-resistance of sea urchin tests (skeletons) in (i) two marine reserves, where predators of sea urchins are relatively common and have initiated a trophic cascade resulting in abundant food for surviving urchins in the form of kelp, and (ii) two adjacent fished areas where predators and kelps are rare. Sea urchins inhabiting protected rocky reefs with abundant predators and food had more crush-resistant tests than individuals on nearby fished reefs where predators and food were relatively rare. A six-month long mesocosm experiment showed that while both food supply and predator cues increased crush-resistance, the positive effect of food supply on crush-resistance was greater. Our results demonstrate a novel mechanism whereby a putative morphological defence in a prey species is indirectly strengthened by predators via cascading predator effects on resource availability. This potentially represents an important mechanism that promotes prey persistence in the presence of predators.

Short larval exposure to low level of copper has long-lasting latent effects on juvenile performance in the sea urchin Evechinus chloroticus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 579:67-79 (2017) - DOI: https://doi.org/10.3354/meps12275 Short larval exposure to low level of copper has long-lasting latent effects on juvenile performance in the sea urchin Evechinus chloroticus Agnes M. Rouchon*, Nicole E. Phillips School of Biological Sciences, Victoria University of Wellington, Wellington 6012, New Zealand *Corresponding author: agnes.rouchon@gmail.com ABSTRACT: Exposure to environmental stressors such as pollutants early in life may have latent effects visible only in later life stages. Sea urchin Evechinus chloroticus larvae were exposed briefly (2 d) to 4 treatments of low levels of copper (2 to 10 µg l-1). Juveniles were re-exposed to a further short pulse of copper (10 µg l-1) to investigate potential resistance to pollution. No major direct effects of larval exposure to copper were observed on larval growth, survival or settlement success. However, complex latent effects started to appear from 8 d post-settlement onwards in individuals exposed as larvae to the highest concentration of copper. Juveniles had strongly impaired growth from 8 to 25 d post-settlement, with average radial length and spine to body ratio decreasing by 24% for both variables. In addition, juveniles previously exposed to the highest tested concentration of copper as larvae were more vulnerable to a subsequent pulse, with up to 4 times higher mortality in groups previously exposed to copper during the larval stage. On the other hand, survivors had a 35% higher growth rate than naive juveniles (i.e. no previous exposure). These results demonstrate that exposure to a concentration of copper similar to that found in many polluted bays and harbours (10 µg l-1) for as little as 48 h in early life impacts juvenile performance and leaves them more vulnerable to a subsequent exposure. This highlights the importance of considering latent effects when evaluating the impacts of pollution. KEY WORDS: Latent effects · Copper toxicity · Sea urchin · Early life stages · Evechinus chloroticus Full text in pdf format Supplementary material PreviousNextCite this article as: Rouchon AM, Phillips NE (2017) Short larval exposure to low level of copper has long-lasting latent effects on juvenile performance in the sea urchin Evechinus chloroticus. Mar Ecol Prog Ser 579:67-79. https://doi.org/10.3354/meps12275 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 579. Online publication date: September 14, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Maternal antioxidant provisioning mitigates pollutant-induced oxidative damage in embryos of the temperate sea urchin Evechinus chloroticus

One mechanism of pollution resistance in marine populations is through transgenerational plasticity, whereby offspring capacity to resist pollution reflects parental exposure history. Our study aimed to establish correlations between oxidative stress biomarkers and key reproductive fitness parameters in the temperate sea urchin Evechinus chloroticus following exposure to dietary polycyclic aromatic hydrocarbons (PAHs). PAH-exposed adults exhibited total gonad tissue concentrations of PAHs in excess of 4 and 5 times baseline levels, for females and males respectively. Antioxidant enzymes were upregulated and oxidative lipid and protein damage to gonad tissues occurred. In addition, early stage offspring reflected maternal antioxidant status, with progeny derived from exposed females demonstrating significantly higher baselines than those derived from control females. Maternal exposure history enhanced the capacity of embryos to minimise oxidative damage to lipids and proteins following exposure to additional PAHs, but provided less of an advantage in protection against oxidative DNA damage. Abnormal embryonic development was largely independent of oxidative damage, remaining high in all embryo populations regardless of parental PAH-history. Overall, results document evidence for maternal transfer of antioxidant potential in E. chloroticus, but imply that a short-term inherited resilience against oxidative stress may not necessarily translate to a fitness or survival gain.

Predation cues rather than resource availability promote cryptic behaviour in a habitat-forming sea urchin.

It is well known that predators often influence the foraging behaviour of prey through the so-called "fear effect". However, it is also possible that predators could change prey behaviour indirectly by altering the prey's food supply through a trophic cascade. The predator-sea urchin-kelp trophic cascade is widely assumed to be driven by the removal of sea urchins by predators, but changes in sea urchin behaviour in response to predators or increased food availability could also play an important role. We tested whether increased crevice occupancy by herbivorous sea urchins in the presence of abundant predatory fishes and lobsters is a response to the increased risk of predation, or an indirect response to higher kelp abundances. Inside two New Zealand marine reserves with abundant predators and kelp, individuals of the sea urchin Evechinus chloroticus were rarer and remained cryptic (i.e. found in crevices) to larger sizes than on adjacent fished coasts where predators and kelp are rare. In a mesocosm experiment, cryptic behaviour was induced by simulated predation (the addition of crushed conspecifics), but the addition of food in the form of drift kelp did not induce cryptic behaviour. These findings demonstrate that the 'fear' of predators is more important than food availability in promoting sea urchin cryptic behaviour and suggest that both density- and behaviourally mediated interactions are important in the predator-sea urchin-kelp trophic cascade.

Acute toxicity of copper, lead, zinc and their mixtures on the sea urchin Evechinus chloroticus

ABSTRACTCoastal pollution is complex, often consisting of multiple contaminants, and it is increasingly recognised that exposure to combinations of pollutants can produce different outcomes than each does separately. This study investigates the toxicity of three major pollutants in coastal environments (copper, lead and zinc) individually and in binary mixtures on larvae of Evechinus chloroticus, a sea urchin endemic to New Zealand. Larval development assays were conducted for 72 h. Median effective concentrations (EC50) for normal larval development for individual metals were 5.4 μg/L Cu, 52.2 μg/L Pb and 27.7 μg/L Zn. Evechinus chloroticus was more sensitive to copper and zinc than most echinoid species tested to date. Effects of metal mixtures were analysed using a toxic unit (TU) approach. Cu + Zn and Cu + Pb had a less-than-additive effect on E. chloroticus larval development. By contrast, Zn + Pb was strictly additive. None of the interactions were strong, with sums of TU ranging from 1.00 to 1.85. These results support the use of criteria based on strictly-additive models to determine whether these three metals exceed water quality thresholds when occurring in a simple mixture.

Genotype-by-environment interactions during early development of the sea urchin Evechinus chloroticus

The increase in seawater temperature due to anthropogenic climate change is likely to affect population persistence and changes in distributional ranges of marine species. Adaptation to warmer environmental conditions will be determined by the presence of tolerant genotypes within a population. The present study determined the genotype-by-environment (G × E) interactions during early development of the New Zealand sea urchin Evechinus chloroticus cultured at 18 °C (mean annual temperature), 21 °C (ambient summer temperature) and 24 °C (+3 °C above ambient summer temperature). The experiment was performed in 3 experimental blocks using gametes from 3 males and 3 females crossed in all combinations (North Carolina II cross-breeding design), resulting in 9 families per experimental block (i.e., total of 27 families). Differences between female and male identities were quantified during cleavage and gastrulation: Reaction norms (i.e., interaction plots) showed a clear G × E interaction, with some genotypes performing better than others at high temperatures. Heritability during gastrulation was 0.51, indicating that 51 % of the variability corresponds to genetic variation. Overall, the present study shows that seawater temperature has a negative effect on early development of E. chloroticus; however, there are resilient genotypes in the studied population that could provide the genetic potential to adapt to future ocean conditions.

Dietary pollutants induce oxidative stress, altering maternal antioxidant provisioning and reproductive output in the temperate sea urchin Evechinus chloroticus

Evidence is growing to suggest that the capacity to withstand oxidative stress may play an important role in shaping life-history trade-offs, although little is known on the relationship in broadcast spawning marine invertebrates. In this group, variation in gamete quantity and quality are important drivers of offspring survival and successful recruitment. Therefore the provisioning of eggs with antioxidants may be an important driver of life history strategies because they play a critical role in preventing damage from reactive oxygen species to macromolecules. In this study, a suite of oxidative stress biomarkers was measured in the gonads and eggs of the sea urchin Evechinus chloroticus exposed to polycyclic aromatic hydrocarbons (PAHs). Links between oxidative stress markers and core components of fitness including fecundity, gamete quality and maternal transfer of antioxidants were assessed. Experimental induction of oxidative stress was achieved via exposure to a mix of four PAHs over a 21-day period. In PAH exposed individuals, we observed a significant upregulation of the antioxidant defence and detoxification enzymes SOD, CAT, GR, GPx and GST, as well as a greater pool of the non-enzymatic antioxidant glutathione in gonad tissue and eggs. In contrast, glutathione redox status was not affected by PAH exposure, with the percentage of reduced glutathione remaining at approximately 80% in both gonad tissue and released eggs. PAH-exposed adults experienced greater than three- and five-fold increases in oxidative protein and lipid damage, respectively, in gonad tissue. In contrast, eggs maintained low levels of damage, not differing from baseline levels found in eggs released from PAH-naïve mothers. PAH exposure also resulted in a 2-fold reduction in fecundity of reproductively mature females but no significant alteration to egg diameter. Although PAH-exposed females released fewer eggs, successful fertilisation of those eggs was slightly enhanced with average rates ranging from 90–99% in comparison to 76–90% in control eggs. Early-stage offspring reflected maternal antioxidant status with populations derived from PAH-exposed mothers demonstrating significantly higher antioxidant levels than those derived from PAH-naïve mothers. This maternally inherited protection enhanced the capacity of embryos to minimise oxidative damage to lipids and proteins during early development but, despite this, did not reduce the proportion of morphological abnormalities in the population. Overall, these findings indicate that when faced with short-term contaminant stress E. chloroticus has the capacity to trade high reproductive output during a spawning event for a greater antioxidant investment in eggs. However, this production of potentially more resilient offspring did not translate to a fitness gain, at least for the early larval stages in the present experimental conditions.

Effects of warm acclimation on physiology and gonad development in the sea urchin Evechinus chloroticus

The physiology of the New Zealand sea urchin Evechinus chloroticus was evaluated through feeding, respiration, growth and gonad growth in adult animals acclimated for 90days at 18°C (annual mean temperature) and 24°C (ambient summer temperature (21°C) +3°C). Measured parameters with representative rates of assimilation efficiency were used to calculate scope for growth (SfG) for each treatment. All physiological parameters were negatively affected at 24°C, showing a decrease in feeding rate which coincided with negative growth and gonad development at the end of the acclimation period, and a decrease in respiration rate suggesting metabolic depression. Histology of gonad samples after the acclimation period also showed no gametic material in animals acclimated at 24°C. All animals acclimated at 24°C had negative growth, differing from the calculated SfG which indicated that the animals had sufficient energy for production. The results suggest that calculated SfG in echinoderms should be used together with actual measurements of growth in individuals as, by itself, SfG may underestimate the actual effect of ocean warming when animals are exposed to stressful conditions. Overall, considering the total loss of reproductive output observed in E. chloroticus at higher temperatures, an increase in seawater temperature could dramatically influence the persistence of northern populations of this species, leading to flow-on effects in the subtidal ecosystem.

Biocontrol of fouling pests: Effect of diversity, identity and density of control agents

Augmentative biocontrol, using native natural enemies, has been suggested as a promising tool to control marine biofouling pests on artificial structures. However, there are still important knowledge gaps to be addressed before biocontrol can be considered as a management tool. In a field experiment on floating marine structures we examined intra- and interspecific consumer interactions among biocontrol agents on different surface orientations. We tested the effect of identity, density and diversity of three invertebrates (the 11-arm seastar Coscinasterias muricata, the sea urchin Evechinus chloroticus and the gastropod Cook's turban Cookia sulcata) to reduce established biofouling and to prevent fouling growth on defouled surfaces. High densities of biocontrol agents were not more effective at fouling control (cover and biomass) than low densities. Nor did multi-species treatments function more effectively than mono-specific ones. However, biocontrol agent identity was important, with the 11-arm seastar and Cook's turban being the most effective at fouling reduction and prevention, respectively. Surface orientation had a strong effect on the effectiveness of control agents, with the best results obtained on vertical compared to diagonal and underside surfaces. This study confirmed the potential of biocontrol as a management tool for marine pest, indicating that identity is more important than richness and density of control agents. It also highlighted the limitations of this approach on diagonal and underside surfaces, where control agents have limited retention ability.

Mechanisms of Nickel Toxicity in the Highly Sensitive Embryos of the Sea Urchin Evechinus chloroticus, and the Modifying Effects of Natural Organic Matter.

A 96 h toxicity test showed that the embryos of the New Zealand sea urchin (Evechinus chloroticus) are the most sensitive of all studied marine species to waterborne nickel (Ni), with the EC50 for the development of fully formed pluteus larvae found to be 14 μg L(-1). Failure to develop a standard larval shape suggested skeletal impairment. Whole body ions (Na, Mg) increased with Ni exposure and calcium influx was depressed. The effects of natural organic matter (NOM) on Ni accumulation and toxicity were also examined in three different seawater sources (nearshore, offshore, and near the outlet of a "brown water" stream). At low dissolved organic carbon (DOC) concentrations the brown water NOM was protective against Ni toxicity, however at higher DOC concentrations it exacerbated developmental toxicity in the presence of Ni. These results show that sea urchin development is highly sensitive to Ni via a mechanism that involves ionoregulatory disturbance, and that Ni toxicity is influenced by environmental factors such as NOM. These data will be critical for the development of water quality guidelines for Ni in the marine environment.

Ontogenetic shifts in resource use by the sea urchin Evechinus chloroticus across an ecotone

Ontogenetic shifts in resource use by the sea urchin Evechinus chloroticus across an ecotone