Posts Tagged 'echinoderms'

Development of the sea urchin Heliocidaris crassispina from Hong Kong is robust to ocean acidification and copper contamination

Highlights

• Ocean acidification will increase the fraction of the most toxic form of copper, increasing its bioavailability to marine organisms
• We tested the hypothesis that copper contaminated waters are more toxic to sea urchin larvae under future pH conditions in three laboratory experiments
• Larvae are robust to the pH and the copper levels we tested (little/no mortality)
• However, significant sub-lethal effects, could have indirect consequences on survival

Abstract

Metallic pollution is of particular concern in coastal cities. In the Asian megacity of Hong Kong, despite water qualities have improved over the past decade, some local zones are still particularly affected and could represent sinks for remobilization of labile toxic species such as copper. Ocean acidification is expected to increase the fraction of the most toxic form of copper (Cu2+) by 2.3-folds by 2100 (pH ≈7.7), increasing its bioavailability to marine organisms. Multiple stressors are likely to exert concomitant effects (additive, synergic or antagonist) on marine organisms.

Here, we tested the hypothesis that copper contaminated waters are more toxic to sea urchin larvae under future pH conditions. We exposed sea urchin embryos and larvae to two low-pH and two copper treatments (0.1 and 1.0 μM) in three separate experiments. Over the short time typically used for toxicity tests (up to 4-arm plutei, i.e. 3 days), larvae of the sea urchin Heliocidaris crassispina were robust and survived the copper levels present in Hong Kong waters today (≤0.19 μM) as well as the average pH projected for 2100. We, however, observed significant mortality with lowering pH in the longer, single-stressor experiment (Expt A: 8-arm plutei, i.e. 9 days). Abnormality and arm asymmetry were significantly increased by pH or/and by copper presence (depending on the experiment and copper level). Body size (d3; but not body growth rates in Expt A) was significantly reduced by both lowered pH and added copper. Larval respiration (Expt A) was doubled by a decrease at pHT from 8.0 to 7.3 on d6. In Expt B1.0 and B0.1, larval morphology (relative arm lengths and stomach volume) were affected by at least one of the two investigated factors.

Although the larvae appeared robust, these sub-lethal effects may have indirect consequences on feeding, swimming and ultimately survival. The complex relationship between pH and metal speciation/uptake is not well-characterized and further investigations are urgently needed to detangle the mechanisms involved and to identify possible caveats in routinely used toxicity tests.

Continue reading ‘Development of the sea urchin Heliocidaris crassispina from Hong Kong is robust to ocean acidification and copper contamination’

Acclimatisation and adaptive capacity of echinoderms in response to ocean acidification and warming

Future ocean acidification and warming pose a substantial threat to the viability of some marine populations. In order to persist, marine species will need to acclimate or adapt to the forecasted changes. Recent research into adaptive capacity of marine species has identified mechanisms of non-genetic inheritance including trans-generational plasticity as important sources of resilience.

Based on literature indicating that echinoderms are tolerant to moderate increases in temperature and seawater pCO2, this study hypothesises three outcomes of long-term exposure to combined ocean acidification and warming:

1. Echinoderms possess the genetic capacity to adapt over long time-scales to
predicted levels of combined ocean acidification and warming.
2. Echinoderms possess the physiological capability to acclimatize to ocean
acidification and warming over long time-scales without a significant cost to
metabolic energy budget.
3. After long-term exposure to ocean acidification and warming, echinoderm parents would alter the phenotype (Anticipatory Parental Effect) of their offspring to increase fitness in the F1 generation in response to the environment to which theparents were exposed.

Continue reading ‘Acclimatisation and adaptive capacity of echinoderms in response to ocean acidification and warming’

Response of sea urchin fitness traits to environmental gradients across the Southern California oxygen minimum zone

Marine calcifiers are considered to be among the most vulnerable taxa to climate-forced environmental changes occurring on continental margins with effects hypothesized to occur on microstructural, biomechanical, and geochemical properties of carbonate structures. Natural gradients in temperature, salinity, oxygen, and pH on an upwelling margin combined with the broad depth distribution (100–1,100 m) of the pink fragile sea urchin, Strongylocentrotus (formerly Allocentrotus) fragilis, along the southern California shelf and slope provide an ideal system to evaluate potential effects of multiple climate variables on carbonate structures in situ. We measured, for the first time, trait variability across four distinct depth zones using natural gradients as analogues for species-specific implications of oxygen minimum zone (OMZ) expansion, deoxygenation and ocean acidification. Although S. fragilis may likely be tolerant of future oxygen and pH decreases predicted during the twenty-first century, we determine from adults collected across multiple depth zones that urchin size and potential reproductive fitness (gonad index) are drastically reduced in the OMZ core (450–900 m) compared to adjacent zones. Increases in porosity and mean pore size coupled with decreases in mechanical nanohardness and stiffness of the calcitic endoskeleton in individuals collected from lower pHTotal (7.57–7.59) and lower dissolved oxygen (13–42 μmol kg−1) environments suggest that S. fragilis may be potentially vulnerable to crushing predators if these conditions become more widespread in the future. In addition, elemental composition indicates that S. fragilis has a skeleton composed of the low Mg-calcite mineral phase of calcium carbonate (mean Mg/Ca = 0.02 mol mol−1), with Mg/Ca values measured in the lower end of values reported for sea urchins known to date. Together these findings suggest that ongoing declines in oxygen and pH will likely affect the ecology and fitness of a dominant echinoid on the California margin.

Continue reading ‘Response of sea urchin fitness traits to environmental gradients across the Southern California oxygen minimum zone’

Starfish larvae lose substantial energy to maintain digestion under ocean acidification conditions

A team of researchers led by Marian Hu from the Institute of Physiology in Christian‐Albrechts‐University, Kiel (Germany) investigated the hidden link between ocean acidification (OA) and digestive functions of microscopic marine larvae. The results of this study are presented in this issue of Acta Physiologica [1]. Ocean acidification ‐ a human‐driven global change in ocean pH – is expected to have multiple impacts on the marine ecosystem and its services but also directly on animal physiology. For instance, Hu and colleagues demonstrated that low‐pH seawater treatment strongly affected the metabolism of the brittlestar Amphiura filliformis and even reduced by 80% arm regeneration following amputation [2]. This team became particularly interested in the metabolic costs of maintaining vital functions such as calcification [3] and digestion [4] under acidified seawater conditions, using echinoderm larvae as their model.

Continue reading ‘Starfish larvae lose substantial energy to maintain digestion under ocean acidification conditions’

Cherchez la femme – impact of ocean acidification on the egg jelly coat and attractants for sperm

The impact of ocean acidification on marine invertebrate eggs and its consequences for sperm chemotaxis are unknown. In the sea urchins Heliocidaris tuberculata and Heliocidaris erythrogramma, with small (93 µm) and large (393 µm) eggs, respectively, we documented the effect of decreased pH on the egg jelly coat, an extracellular matrix that increases target size for sperm and contains sperm-attracting molecules. In near-future conditions (pH 7.8, 7.6), the jelly coat of H. tuberculata decreased by 11% and 21%, reducing egg target size by 9% and 17%, respectively. In contrast, the egg jelly coat of H. erythrogramma was not affected. The reduction in the jelly coat has implications for sperm chemotaxis in H. tuberculata. In the presence of decreased pH and egg chemicals, the sperm of this species increased their velocity, motility and linearity, behaviour that was opposite to that seen for sperm exposed to egg chemicals in ambient conditions. Egg chemistry appears to cause a reduction in sperm velocity where attractants guide the sperm in the direction of the egg. Investigation of the effects of decreased pH on sperm isolated from the influence of egg chemistry does not provide an integrative assessment of the effects of ocean acidification on sperm function. Differences in the sensitivity of the jelly coat of the two species is likely associated with egg evolution in H. erythrogramma. We highlight important unappreciated impacts of ocean acidification on marine gamete functionality, and insights into potential winners and losers in a changing ocean, pointing to the advantage conveyed by the evolution of large eggs.

Continue reading ‘Cherchez la femme – impact of ocean acidification on the egg jelly coat and attractants for sperm’

Building global change resilience: concrete has the potential to ameliorate the negative effects of climate-driven ocean change on a newly-settled calcifying invertebrate

Highlights 

• Coastal protection structures need to be upgraded in response to rising sea levels.
• Upgrades using pH-buffering concrete may shield colonizers from ocean acidification.
• We settled sea urchins on concrete and rocks in ocean conditions predicted by 2100.
• Concrete inhibited settlement, but had positive effects on growth and survival.
• Concrete shows potential for responding to sea level rise and ocean climate change.

Abstract

Global climate change is driving sea level rise and increasingly frequent storm events, which are negatively impacting rapidly-growing coastal communities. To mitigate these impacts, coastal infrastructure must be further protected by upgrading hard defences. We propose that incorporating pH-buffering materials into these upgrades could safeguard marine organisms from the adverse effects of ocean acidification and ocean warming during the vulnerable transition from planktonic larvae to benthic juveniles. To test this, we examined the effects of ocean warming (24 or 27 °C), ocean acidification (pH 8.1, 7.9, 7.7), and substratum (concrete, greywacke, granite) in all combinations on the settlement success of an ecologically and commercially important sea urchin, Tripneustes gratilla. Low pH (7.9, 7.7) generally reduced the quantity and size of juveniles four weeks post-settlement, although this was partially ameliorated by increased temperature (24 vs. 27 °C). In the warmed and acidified treatments, settlement rates were lower on concrete than granite or greywacke, but two weeks post-settlement, juveniles on concrete were larger, and had longer spines and higher survival rates than on greywacke or granite, respectively. The benefits provided by concrete to newly-settled juveniles may be related to alkali chemicals leaching from concrete buffering low pH conditions in surrounding seawater and/or increased availability of bicarbonate in the boundary layers around its surface. Our results highlight the potential for pH-buffering materials to assist marine organisms in coping with the effects of changing ocean conditions, but further research is required to understand the generality and mechanism(s) driving the beneficial effects of concrete and to test pH-buffering materials in the field.

Continue reading ‘Building global change resilience: concrete has the potential to ameliorate the negative effects of climate-driven ocean change on a newly-settled calcifying invertebrate’

Relación del pH y oxígeno disuelto de fondo con la distribución del bentos calcificante de la plataforma Centro – Norte Peruana (in Spanish)

The present study aims to examine the combined influence of oxygen deficiency
and low pH conditions on the community parameters and the composition of the
calcifying macrobenthos, besides analyzing its spatial structure, between 2007
and 2014 in the north central Peruvian shelf (3 ° -9 ° S). The decadal changes of
the calcifying macrobenthos were also evaluated against the bottom dissolved
oxygen content between 1976 and 2015. For the bottom pH, simulated data from
the ROMS-PISCES model, which was previously validated and corrected, were
used at a spatial resolution of 1/9°. The oxygen and pH conditions were classified
into four combined categories, evaluating the community parameters of the
calcifying macrobenthos as dependent variables. The highest abundances of
calcifying macrobenthos were recorded south of 6°S, where there is a greater
organic enrichment and oxygen deficiency. Species richness of the calcifying
macrobenthos showed the lowest values at both low pH and oxygen conditions.
Also, diversity indexes were the highest when oxygen was high and pH low. The
bivalve Solemya sp. was the only species that tolerated both hypoxic and low pH
conditions. Finally, bottom oxygenation towards the period 1995 – 2009
corresponds to the increase of crustacean abundance. It is necessary to review
the calcifying macrobenthos diversity and adaptations associated with upwelling
areas.

Continue reading ‘Relación del pH y oxígeno disuelto de fondo con la distribución del bentos calcificante de la plataforma Centro – Norte Peruana (in Spanish)’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,113,504 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book