The population dynamics and recruitment pattern of the phoronid, Phoronopsis viridis

A dominant organism on intertidal Pacific Coast sandflats is the lophophorate Phoronopsis viridis Hilton. This suspension feeder builds a stiff, sandy tube, 3 mm wide and up to 20 cm long and usually lying within 6 cm of the surface (Johnson 1967a). Phoronopsis viridis is found over large areas and tidal ranges of sandflats in aggregate densities of over 21,000 phoronids per m2 (Ronan 1978). On Lawson\u27s Flat, the location of the present study, the areas of highest density of P. viridis have been known to persist for over 20 years (Steven Obrebski, personal communication). The factors accounting for the persistence of these dense phoronid populations have not been studied although four hypotheses have been proposed (see Ronan 1975, 1978). These are: 1) dense clusters of adult phoronids increase the probability of successful gamete fertilization; 2) high densities of phoronids stablize the sediment, thus limiting the movement of large burrowing in fauna that are potentially destructive to phoronids (Ronan 1975); 3) a dense canopy of lophophores slows currents over the sediment surface, increasing the deposition of food items; and 4) clustering limits the effects of predation. The sudden retraction of a lophophore in response to a disturbance results in withdrawal of neighboring phoronids in the area of the disturbance (Ronan 1978). In order to evaluate the adaptive significance of population persistence it is crucial to understand the mechanism by which dense populations :persist. Therefore the purpose of this study is not to assess the adaptive significance of clustering, but rather to determine what mechanisms might explain the persistence of dense phoronid populations.. Consequently, this study is more applicable to an ecological time scale than an *evolutionary one. In this study the population dynamics and recruitment pattern of P. viridis is described with reference to the mechanism which enables persistence of dense phoronid areas. In addition, the effects of food abundance and the reworking activity of the surface deposit feeder, Axiothella rubrocincta Johnson, a maldanid polychaete, on P. viridis density and recruitment are measured

Timing of successful settlement : demonstration of a recruitment window in the barnacle Semibalanus balanoides

Author Posting. © Inter-Research, 2006. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 320 (2006): 233-237, doi:10.3354/meps320233.Recruitment is a key factor in benthic population dynamics, and spatial and temporal processes that affect settlement may determine recruitment; however, temporal processes are not well understood. We tested whether the date that recruits settle is a random sample within the settlement season by measuring daily settlement of the barnacle Semibalanus balanoides throughout the entire settlement season. A total of 2721 barnacle larvae settled during 89 d on 12 quadrats. Individual settlers were tracked to reproductive age (11 mo after settlement); only 8 survived to reproduction. Survivors settled within a narrow 21 d recruitment window, a period shorter than expected by chance. The concept of a recruitment window has broad implications in studying benthic recruitment and population dynamics. Focus on the recruitment window when it is narrow could simplify the study of recruitment, since fewer factors would have to be considered.This work was supported by the US NSF (OCE-9986627 and OCE- 0083976)

Barnacle larvae in ice : survival, reproduction, and time to post settlement metamorphosis

Author Posting. © The Author(s), 2005. This is the author's version of the work. It is posted here by permission of American Society of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 50 (2005): 1520-1528.Late stage larvae (cyprids) of the barnacle Semibalanus balanoides frequently encounter freezing conditions along the northwest Atlantic coast. S. balanoides cyprids survived for more than 4 weeks embedded in sea ice, and a significant fraction of larvae held in ice up to 2 weeks successfully settled and metamorphosed after thawing. Larvae that completed metamorphosis continued to develop and reproduce. In settlement experiments with cyprids of known age and where settled cyprids were removed every other day from the experimental containers, cyprids held in ice for 2 weeks settled and metamorphosed more than nonfrozen larvae. Mean time to metamorphosis was longer for frozen cyprids than for nonfrozen ones, and maximum time to metamorphosis was 38 d for cyprids held in sea ice for 2 weeks and 26 d for cyprids in nonfrozen treatments. Larval tolerance to freezing conditions greatly expands the environmental tolerance repertoire of marine invertebrates and may help explain the ecological success of this widespread intertidal species.This work was supported by the U.S. National Science Foundation (OCE-9986627 and OCE-0083976)

Complexity and simplification in understanding recruitment in benthic populations

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Population Ecology 51 (2009): 17-32, doi:10.1007/s10144-008-0118-0.Research of complex systems and problems, entities with many dependencies, is often reductionist. The reductionist approach splits systems or problems into different components, and then addresses these components one by one. This approach has been used in the study of recruitment and population dynamics of marine benthic (bottom dwelling) species. Another approach examines benthic population dynamics by looking at a small set of processes. This approach is statistical or model oriented. Simplified approaches identify “macrcoecological” patterns or attempt to identify and model the essential, “first order” elements of the system. The complexity of the recruitment and population dynamics problems stems from the number of processes that can potentially influence benthic populations, including (1) larval pool dynamics, (2) larval transport, (3) settlement, and (4) post-settlement biotic and abiotic processes, as well as larval production. Moreover, these processes are non-linear, some interact, and they may operate at disparate scales. This contribution discusses reductionist and simplified approaches to study benthic recruitment and population dynamics of bottom dwelling marine invertebrates. We first address complexity in two processes known to influence recruitment, larval transport, and post settlement survival to reproduction, and discuss the difficulty in understanding recruitment by looking at relevant processes individually and in isolation. We then address the simplified approach, which reduces the number of processes and makes the problem manageable. We discuss how simplifications and “broad-brush first order approaches” may muddle our understanding of recruitment. Lack of empirical determination of the fundamental processes often results in mistaken inferences, and processes and parameters used in some models can bias our view of processes influencing recruitment. We conclude with a discussion on how to reconcile complex and simplified approaches. Although it appears impossible to achieve a full mechanistic understanding of recruitment by studying all components of the problem in isolation, we suggest that knowledge of these components is essential for simplifying and understanding the system beyond probabilistic description and modeling.We wish to thank WHOI’s Ocean Life Institute for suppor

Flocs, flows, and mechanisms decoupling larval supply from settlement

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2012. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 57 (2012): 936-944, doi:10.4319/lo.2012.57.4.0936.Larval supply, settlement (24 h), and recruitment were measured simultaneously with flow and flocculated particulates (flocs) in a muddy, coastal embayment. Fortuitous observations indicated that flocs drifting above the bed touched down at slack tide. Unexpectedly, results showed that larval supply did not portend settlement for the two most abundant polychaetes, Mediomastus ambiseta (resident mud dweller) and Sabellaria vulgaris (nonresident sand dweller). Both variables fluctuated widely and were decoupled. Colonization of mud vs. sand trays was not significantly different, also due to high variances. A statistical power analysis indicated that resolving selectivity would require 45 (median) paired, replicate treatments. Time series of near-bed planktonic larvae showed sizeable and sporadic spikes. Even 24-h means failed to predict settlement. Sabellaria was numerous in zooplankton pump collections, rare in trays, and nonexistent in ambient sediments. In contrast, Mediomastus was absent from pump samples, but dominated mud trays and bottom cores. Floc contents, however, lend insight into these distributions. Densities (of order 105 m-3) of Sabellaria and Mediomastus in flocs greatly exceeded those in tray and pump samples (of order 103 m-3). Located between the water column and seafloor, organic-rich flocs may offer transient larvae food, shelter, transport, and perusal of settlement sites. When aggregates touch down, entrained Mediomastus might exit upon contact with suitable ambient sediments, whereas nonresident Sabellaria remain suspended. Flocs may thus play a critical role in shaping connectivity and structuring species distributions.This study was supported by the National Science Foundation (Division of Ocean Sciences, OCE 08-52361) and the University of California at Los Angeles Council on Research

Larval settlement in flocculated particulates

Author Posting. © The Authors, 2008. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 66 (2008): 275-297, doi:10.1357/002224008785837167.Planktonic larval settlement can be a major determinant of population and community dynamics. Settlement templates of benthic invertebrates have been attributed to biological, chemical, and hydrodynamic mechanisms. Completely unexplored, however, is the role of patchy, but widespread, flocculated particulates (“floc”) that intermittently rest on substrate surfaces. Motivated by observations of very high (of order 106 m-3) larval/postlarval densities in floc from a coastal embayment, this study experimentally identified physical and behavioral mechanisms responsible for these associations. In annular-flume studies, sediment cores were mounted flush with the channel bottom, serving as the floc source. Larval (Capitella sp. I, a polychaete worm) distributions in the flume were consistent with predictions for transported particulates. Floc and larvae accumulated at the channel inner corner in high flows (shear velocities, u*, of 0.8 and 1.6 cm s-1), but not in low flows (u* of 0, 0.2 and 0.4 cm s-1). Inner-corner concentrations of larvae/floc resulted from a predictable, cross-channel, bottom flow in that direction. In still-water behavioral assays, there were no significant differences in percent metamorphosis among flocs fabricated from particulate-laden seawater, conspecific fecal pellets (compact floc) and organic-rich sediment. Surficial aggregates clearly were acceptable settlement substratum. This study is the first to show that settling larvae associate with surficial aggregates via both physical and behavioral mechanisms. Floc may be a transient larval venue facilitating habitat search, providing nutrition, or offering protection from predators. Alternatively, it could confer high mortality, reducing larval flux to the bed. Associations between larvae and floc do not supersede established mechanisms of habitat selection. They just thicken the plot.This study was supported by the National Science Foundation (OCE 97-29972 and OCE 02-42321), NOAA California Sea Grant College Program (R/F-197) and the UCLA Council on Research

The role of season and salinity in influencing barnacle distributions in two adjacent coastal mangrove lagoons

Author Posting. © University of Miami - Rosenstiel School of Marine and Atmospheric Science, 2011. This article is posted here by permission of University of Miami - Rosenstiel School of Marine and Atmospheric Science for personal use, not for redistribution. The definitive version was published in Bulletin of Marine Science 87 (2011): 275-299, doi:10.5343/bms.2010.1022.Barnacles are often abundant on roots and branches of mangrove trees in tidal channels and coastal lagoons of the Pacific coast of Panama. Yet, in some coastal lagoons, barnacles are absent. We investigated pre- and post-settlement factors that affect barnacle distributions in two adjacent coastal lagoons in Bahía Honda, Panama, one with moderate to large barnacle populations, and the other with nearly non-existent populations. Although mean barnacle recruitment was higher on mangrove root segments during the dry season (December-April) than in the wet season (May-November), it was not significantly different between the two coastal lagoons. The coastal lagoon with fewer barnacles is considered an estuary, with high freshwater flow and low salinities (0.1) during the wet season that were lethal to barnacle nauplii and cyprids. Furthermore, coastal water was not observed to enter the lagoon, even during flood tides. In contrast, more barnacles were found in the lagoon with higher salinities (8.5). During the dry season, freshwater flow was greatly reduced in both lagoons, resulting in a similar salinity range (22-33). We conclude that the lack of barnacles in the estuarine coastal lagoon is largely due to high flushing rates and low salinities that reduce larval concentrations during the wet season. Moreover, low adult abundance in the lagoon's interior may further reduce larval supply and settlement.Finally, we would like to thank the Ocean Life Institute of the Woods Hole Oceanographic Institution for funding to JP to complete research in the Liquid Jungle Lab.2014-07-0

Cytochrome P450 diversity and induction by gorgonian allelochemicals in the marine gastropod Cyphoma gibbosum

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Ecology 10 (2010): 24, doi:10.1186/1472-6785-10-24.Intense consumer pressure strongly affects the structural organization and function of marine ecosystems, while also having a profound effect on the phenotype of both predator and prey. Allelochemicals produced by prey often render their tissues unpalatable or toxic to a majority of potential consumers, yet some marine consumers have evolved resistance to host chemical defenses. A key challenge facing marine ecologists seeking to explain the vast differences in consumer tolerance of dietary allelochemicals is understanding the biochemical and molecular mechanisms underlying diet choice. The ability of marine consumers to tolerate toxin-laden prey may involve the cooperative action of biotransformation enzymes, including the inducible cytochrome P450s (CYPs), which have received little attention in marine invertebrates despite the importance of allelochemicals in their evolution. Here, we investigated the diversity, transcriptional response, and enzymatic activity of CYPs possibly involved in allelochemical detoxification in the generalist gastropod Cyphoma gibbosum, which feeds exclusively on chemically defended gorgonians. Twelve new genes in CYP family 4 were identified from the digestive gland of C. gibbosum. Laboratory-based feeding studies demonstrated a 2.7- to 5.1-fold induction of Cyphoma CYP4BK and CYP4BL transcripts following dietary exposure to the gorgonian Plexaura homomalla, which contains high concentrations of anti-predatory prostaglandins. Phylogenetic analysis revealed that C. gibbosum CYP4BK and CYP4BL were most closely related to vertebrate CYP4A and CYP4F, which metabolize pathophysiologically important fatty acids, including prostaglandins. Experiments involving heterologous expression of selected allelochemically-responsive C. gibbosum CYP4s indicated a possible role of one or more CYP4BL forms in eicosanoid metabolism. Sequence analysis further demonstrated that Cyphoma CYP4BK/4BL and vertebrate CYP4A/4F forms share identical amino acid residues at key positions within fatty acid substrate recognition sites. These results demonstrate differential regulation of CYP transcripts in a marine consumer feeding on an allelochemical-rich diet, and significantly advance our understanding of both the adaptive molecular mechanisms that marine consumers use to cope with environmental chemical pressures and the evolutionary history of allelochemical-metabolizing enzymes in the CYP superfamily.Financial support for this work was provided by the Ocean Life Institute Tropical Research Initiative Grant (WHOI) to KEW and MEH; the Robert H. Cole Endowed Ocean Ventures Fund (WHOI) to KEW; the National Undersea Research Center - Program Development Proposal (CMRC-03PRMN0103A) to KEW and a National Science Foundation Graduate Research Fellowship to KEW

The characteristics and dynamics of wave-driven flow across a platform coral reef in the Red Sea

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 1360–1376, doi:10.1002/2015JC011141.Current dynamics across a platform reef in the Red Sea near Jeddah, Saudi Arabia, are examined using 18 months of current profile, pressure, surface wave, and wind observations. The platform reef is 700 m long, 200 m across with spatial and temporal variations in water depth over the reef ranging from 0.6 to 1.6 m. Surface waves breaking at the seaward edge of the reef cause a 2–10 cm setup of sea level that drives cross-reef currents of 5–20 cm s−1. Bottom stress is a significant component of the wave setup balance in the surf zone. Over the reef flat, where waves are not breaking, the cross-reef pressure gradient associated with wave setup is balanced by bottom stress. The quadratic drag coefficient for the depth-average flow decreases with increasing water depth from Cda = 0.17 in 0.4 m of water to Cda = 0.03 in 1.2 m of water. The observed dependence of the drag coefficient on water depth is consistent with open-channel flow theory and a hydrodynamic roughness of zo = 0.06 m. A simple one-dimensional model driven by incident surface waves and wind stress accurately reproduces the observed depth-averaged cross-reef currents and a portion of the weaker along-reef currents over the focus reef and two other Red Sea platform reefs. The model indicates the cross-reef current is wave forced and the along-reef current is partially wind forced.This research is based on work supported by awards USA 00002 and KSA 00011 KAUST. K. Davis was supported by a WHOI Postdoctoral Fellowship. T. Farrar was partly supported by NSF grant OCE-1435665. S. Lentz was partly supported by NSF grants OCE-1332646 and OCE-1357290.2016-08-1

Impacts of multiple stressors on a benthic foraminiferal community: a long-term experiment assessing response to ocean acidification, hypoxia and warming

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bernhard, J. M., Wit, J. C., Starczak, V. R., Beaudoin, D. J., Phalen, W. G., & McCorkle, D. C. Impacts of multiple stressors on a benthic foraminiferal community: a long-term experiment assessing response to ocean acidification, hypoxia and warming. Frontiers in Marine Science, 8, (2021): 643339, https://doi.org/10.3389/fmars.2021.643339.Ocean chemistry is changing as a result of human activities. Atmospheric carbon dioxide (CO2) concentrations are increasing, causing an increase in oceanic pCO2 that drives a decrease in oceanic pH, a process called ocean acidification (OA). Higher CO2 concentrations are also linked to rising global temperatures that can result in more stratified surface waters, reducing the exchange between surface and deep waters; this stronger stratification, along with nutrient pollution, contributes to an expansion of oxygen-depleted zones (so called hypoxia or deoxygenation). Determining the response of marine organisms to environmental changes is important for assessments of future ecosystem functioning. While many studies have assessed the impact of individual or paired stressors, fewer studies have assessed the combined impact of pCO2, O2, and temperature. A long-term experiment (∼10 months) with different treatments of these three stressors was conducted to determine their sole or combined impact on the abundance and survival of a benthic foraminiferal community collected from a continental-shelf site. Foraminifera are well suited to such study because of their small size, relatively rapid growth, varied mineralogies and physiologies. Inoculation materials were collected from a ∼77-m deep site south of Woods Hole, MA. Very fine sediments (<53 μm) were used as inoculum, to allow the entire community to respond. Thirty-eight morphologically identified taxa grew during the experiment. Multivariate statistical analysis indicates that hypoxia was the major driving factor distinguishing the yields, while warming was secondary. Species responses were not consistent, with different species being most abundant in different treatments. Some taxa grew in all of the triple-stressor samples. Results from the experiment suggest that foraminiferal species’ responses will vary considerably, with some being negatively impacted by predicted environmental changes, while other taxa will tolerate, and perhaps even benefit, from deoxygenation, warming and OA.This work was supported by the US NSF SEES-OA grant OCE-1219948 to JB and the Investment in Science Program at WHOI. DM also received support from the NSF Independent Research and Development Program