Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

Supporting Online Material for Spreading Dead Zones and Consequences for Marine Ecosystems

Newly settled invertebrates usually are subject to high rates of mortality (Type 111 survivorship). Therefore, knowledge of early post-settlement events is critical in determ~nlng if and when patterns of abundance and distribution of juveniles reflect settlement patterns. Causes of mortality of early juvenile invertebrates include delay of metamorphosis, biological disturbance, physical disturbance and hydrodynamics, physiological stress, predation, and competition. Predation is the best documented cause of early n~ortallty, particularly for mobile species. Other possible causes which have not yet been investigated are developmental abnormalities, insufficient energy reserves, disease and parasitism In most studies of sessile invertebrates, early post-settlement mortality did not obscure the relationship between recruit and settler abundance. This relatlonsh~p appears to be more varlable among mobile species for which migrat~on also can modify the distnbution of settlers. There is still insufficient data to support general conclusions about the conditions under which recruitment rate can be predicted from settlement rate. Studies have found evidence of the effects of both settlement and early post-settlement mortality on the dlstributlon of some sessile species at small spatial scales, but mortality appears to have less influence a t larger scales. Much of the present knowledge of the early postsettlement period has come from studies of barnacles and ascidians and more information is needed for other groups of benthic marine invertebrates, particularly mobile species. The relative importance of mortality during the early post-settlement period compared to other life history stages can only be detel-mined in studies which examlne several stages.

/pdf/role-of-early-post-settlement-mortality-in-recruitment-of-vcen6f4utw.pdf

Role of early post-settlement mortality in recruitment of benthic marine invertebrates

Natural Chemical Cues for Settlement and Metamorphosis of Marine-Invertebrate Larvae

Background: Human activities have increased atmospheric concentrations of carbon dioxide by 36% during the past 200 years. One third of all anthropogenic CO2 has been absorbed by the oceans, reducing pH by about 0.1 of a unit and significantly altering their carbonate chemistry. There is widespread concern that these changes are altering marine habitats severely, but little or no attention has been given to the biota of estuarine and coastal settings, ecosystems that are less pH buffered because of naturally reduced alkalinity. Methodology/Principal Findings: To address CO2-induced changes to estuarine calcification, veliger larvae of two oyster species, the Eastern oyster (Crassostrea virginica), and the Suminoe oyster (Crassostrea ariakensis) were grown in estuarine water under four pCO2 regimes, 280, 380, 560 and 800 matm, to simulate atmospheric conditions in the pre-industrial era, present, and projected future concentrations in 50 and 100 years respectively. CO2 manipulations were made using an automated negative feedback control system that allowed continuous and precise control over the pCO2 in experimental aquaria. Larval growth was measured using image analysis, and calcification was measured by chemical analysis of calcium in their shells. C. virginica experienced a 16% decrease in shell area and a 42% reduction in calcium content when preindustrial and end of 21 st century pCO2 treatments were compared. C. ariakensis showed no change to either growth or calcification. Both species demonstrated net calcification and growth, even when aragonite was undersaturated, a result that runs counter to previous expectations for invertebrate larvae that produce aragonite shells. Conclusions and Significance: Our results suggest that temperate estuarine and coastal ecosystems are vulnerable to the expected changes in water chemistry due to elevated atmospheric CO2 and that biological responses to acidification, especially calcifying biota, will be species-specific and therefore much more variable and complex than reported previously.

/pdf/shellfish-face-uncertain-future-in-high-co2-world-influence-1pvsswef5g.pdf

Shellfish Face Uncertain Future in High CO2 World: Influence of Acidification on Oyster Larvae Calcification and Growth in Estuaries

https://pubag.nal.usda.gov/download/29264/PDF

The ecological role of bivalve shellfish aquaculture in the estuarine environment: A review with application to oyster and clam culture in West Coast (USA) estuaries

The prey and size-class preferences of four marine epibenthic predators was examined in a laboratory study by determining the mortality rates of four commercial bivalve species in 4-d trials where predators were present or absent. Bivalve species used were quahogs (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), blue mussels (Mytilus edulis) and soft-shell clams (Mya arenaria). Prey size-classes investigated were 0–15, 15–25 and 25–40 mm. A first set of experiments compared the mortality rates of prey in the presence of the invasive green crab (Carcinus maenas) and the native rock crab (Cancer irroratus). The second set of experiments compared the predation behavior of the green crab, the common starfish (Asterias vulgaris) and the moon snail (Euspira heros). Single- and multiple-choice experiments were carried out in relation to the prey species being challenged by the predator. Results from the first set of experiments showed that green crabs preyed on all prey species from all...

https://bioone.org/journals/Journal-of-Shellfish-Research/volume-24/issue-2/0730-8000(2005)24[579:PPOTIG]2.0.CO;2/PREDATION-POTENTIAL-OF-THE-INVASIVE-GREEN-CRAB-CARCINUS-MAENAS-AND/10.2983/0730-8000(2005)24[579:PPOTIG]2.0.CO;2.pdf

Predation potential of the invasive green crab (carcinus maenas) and other common predators on commercial bivalve species found on prince edward island

Conceptual models in manne benthic ecology have been reinforced with the use of larval recruitment as a key factor to predict fluctuations in the abundance and distnbution of sessile adult populations In turn, larval recruitment is determined uslng vanous indicators of planktonic larval abundance (larval supply) Based on plankton and settlement data collected over an entire settlement penod of the barnacle Sem~balanus balanoldes, we explore the vanability in the strength of the relationships between the abundance of newly settled individuals sampled dally at 3 shore levels and the daily larval abundance at 3 different depths over a 10 d study period The best correlation was obtained between the number of larvae collected near the bottom and the number of spat sampled in the low intertidal More than 75% of the vanability in the abundance of newly settled spat In the lower intertidal was explained by vanations in the larval abundance near the bottom Larval abundance integrated over the entire water column explained -50% of the vanability In low shore settlement, but failed to be significant All other comparisons showed a lack of correlations Our approach demonstrates that indicators of larval supply must be carefully and solidly documented to reflect the relationships between abundance of competent larvae settlement intensity and subsequently recruitment

/pdf/use-of-larval-supply-in-benthic-ecology-testing-correlations-68cpjvep80.pdf

Use of larval supply in benthic ecology: testing correlations between larval supply and larval settlement

The vertical distribution of veligers, pediveligers and post-larvae of the mussel Mytilus edulis L. was examined in Kandalakshsky Gulf (White Sea), Russia. Plankton samples showed that about 65% of all planktonic larvae were collected from a depth of 1.5 to 3 m. Maximum numbers of veligers were found at 3 m, immediately above the thermocline. The vertical distribution of veligers was stable throughout the study. The vertical distribution of pediveligers, however, varied over time. Pediveligers were mostly observed at 3 m before settlement peaked while they migrated closer to the water surface (1.5 m) during the settlement period. Pediveliger concentrations were correlated posi- tively with small phytoplanktonic cell (<150 µm) and dissolved organic matter concentrations before settlement peaked. Both factors were correlated negatively with pediveliger concentrations during the settlement period. Newly settled post-larvae mainly colonized settlement panels situated at 1.5 m below the water surface (ca 70% of total post-larvae abundance). These results support the hypothe- sis that planktonic larvae of M. edulis change their vertical distribution in relation to larval stages, which in turn, increases settlement success.

/pdf/larval-and-post-larval-vertical-distribution-of-the-mussel-15x4vep9gn.pdf

Larval and post-larval vertical distribution of the mussel Mytilus edulis in the White Sea

The roles of larval supply, selection of habitat, availability of space, larval physiological condition, and early post-settlement mortality in determining vertical distribution patterns of the barnacle Semibalanus balanoides (L.) were simultaneously examined in Passamaquoddy Bay, New Brunswick, Canada. Pump samples and settlement surveys showed that about 60% of planktonic cyprids were collected from 1.5 to 4.0 m depth, while over 90% of newly settled cyprids colonized low intertidal levels. Selection of habitat by cyprids and patterns of settlement were studied using precolonized planks that had been previously placed to obtain various periphyton gradients. These planks precolonized at the low, mid-, and high intertidal levels and placed in different orientations, induced variations in the distribution of newly settled cyprids. For example, vertical planks turned upside down had fewer settlers at low intertidal levels compared to surfaces maintained in the same orientation at the same level. When placed horizontally at the same level, sections precolonized at the low intertidal level collected more larvae than sections initially placed at the high and mid-intertidal levels. We used the triacylglycerol/cholesterol ratio (TAG/CHOL) as a measure of physiological condition in planktonic and newly settled cyprids, and newly metamorphosed spat. The TAG/CHOL ratio in planktonic cyprids decreased over the sampling period, but there was no variability with position in the water column. For newly settled cyprids and newly metamorphosed spat, the TAG/CHOL ratio increased with decreasing intertidal level. Quadrats freed of conspecific adults were colonized by more cyprids than were uncleared controls. Early post-settlement mortality was greater in uncleared than in cleared quadrats, but this effect varied with intertidal level. Early post-settlement mortality increased with increasing intertidal level in cleared quadrats, while it did not significantly vary in uncleared controls. The present study shows that the vertical distribution of S, balanoides on the shore results from a complex relationship involving larval supply, selection of habitat, availability of space, and early post-settlement mortality. We also present the first evidence of correlations between larval physiological condition and early vertical distribution in S. balanoides.

/pdf/intertidal-barnacle-distribution-a-case-study-using-multiple-45sb4b75z7.pdf

Gilles Miron

Papers

Predation potential of the invasive green crab (carcinus maenas) and other common predators on commercial bivalve species found on prince edward island

Use of larval supply in benthic ecology: testing correlations between larval supply and larval settlement

Larval and post-larval vertical distribution of the mussel Mytilus edulis in the White Sea

Intertidal barnacle distribution : a case study using multiple working hypotheses

Reproduction and early life history of an invasive ascidian Styela clava Herdman in Prince Edward Island, Canada