Internal tidal bores in the nearshore: Warm-water fronts, seaward gravity currents and the onshore transport of neustonic larvae

Nearshore temperature fluctuations are associated with energetic cross-shore two-way flows that influence the onshore transport of neustonic larvae. Water temperature near the surface and bottom at two nearshore stations off southern California (6 and 15 m water depth, respectively) can drop sharply and subsequently rise. Two or more consecutive drops and rises can occur at diurnal or semidiurnal periodicities. The temperature increases may be accompanied by energetic seaward bottom currents together with sharp-edged warm-water fronts. (Warm-water fronts are defined here as linear seasurface features dividing parcels of water of different temperature.) Shoreward-moving surface fronts divided bodies of water of different surface temperature, where the coldest water body was inshore. Fronts disappeared at (or close to) the surf zone. The sharp drops in water temperature are interpreted as the onshore advection of subsurface water by large internal tidal bores, and it is concluded that the sudden increases in temperature and cross-shore advection are epiphenomena of internal tidal bores. Internal tidal bores have been invoked previously to explain the onshore transport of water-column larvae. This study tests the hypothesis that shoreward surface flow, an epiphenomenon of internal tidal bores, transports neustonic larvae in warm-water fronts. Five warm-water fronts were sampled in shallow water (about 6 m) for temperature and fish and crab larvae in June-July 1992. These larvae were more abundant in fronts than in parcels of water preceding or following the front. Peaks in larval abundance were accompanied by a sharp rise in temperature, in itself evidence for onshore transport of surface water. It is concluded that both warm-water fronts and internal tidal bores play a key role in the exchange across the shelf of material and water properties, and that internal tidal-bore phenomena explain well the transport of both water-column and neustonic larvae in different habitats

Plankton accumulation and transport in propagating nonlinear internal fronts

Author Posting. © Sears Foundation for Marine Research, 2007. 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 65 (2007): 117-145, doi:10.1357/002224007780388702.Accumulation and transport of plankton in fronts propagating across-shore is a process of considerable ecological importance for many inhabitants of the littoral zone, since it links the offshore larval pool with the juvenile and adult inshore habitat. Several field studies have shown that larval plankton accumulates in fronts, but have failed to give a conclusive proof that effective Lagrangian transport takes place. A few process-oriented numerical studies have lent support to the idea, but the scope of their results is limited by the two-dimensional nature of the flows considered and by the simple model used to account for the behavior of plankton. In this paper, we relax both constraints. We solve the three-dimensional Navier-Stokes equation to compute the time dependent velocity field, and we use an empirically based model for the behavior of plankton. Our results show that accumulation and transport is possible, even for larvae characterized by sustained swimming speeds that are small compared with the speed of propagation of the front. We introduce a simple model to characterize the accumulation along the front, which includes both entrainment and detrainment. The model accurately represents accumulation calculated from the numerical runs, and provide a simple tool to estimate transport under a variety of circumstances. We also investigate the spatial distribution of plankton along and across the front and show that it is very patchy and dependent on the swimming speed of plankton, with important implications for interpreting results from field experiments

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)

Larval transport and dispersal in the coastal ocean and consequences for population connectivity

Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 3 (2007): 22-39.Many marine species have small, pelagic early life stages. For those species, knowledge of population connectivity requires understanding the origin and trajectories of dispersing eggs and larvae among subpopulations. Researchers have used various terms to describe the movement of eggs and larvae in the marine environment, including larval dispersal, dispersion, drift, export, retention, and larval transport. Though these terms are intuitive and relevant for understanding the spatial dynamics of populations, some may be nonoperational (i.e., not measurable), and the variety of descriptors and approaches used makes studies difficult to compare. Furthermore, the assumptions that underlie some of these concepts are rarely identified and tested. Here, we describe two phenomenologically relevant concepts, larval transport and larval dispersal. These concepts have corresponding operational definitions, are relevant to understanding population connectivity, and have a long history in the literature, although they are sometimes confused and used interchangeably. After defining and discussing larval transport and dispersal, we consider the relative importance of planktonic processes to the overall understanding and measurement of population connectivity. The ideas considered in this contribution are applicable to most benthic and pelagic species that undergo transformations among life stages. In this review, however, we focus on coastal and nearshore benthic invertebrates and fishes.We thank the National Oceanic and Atmospheric Administration, the National Science Foundation, and the Woods Hole Oceanographic Institution for supporting our work

Turbidity triggers larval release by the intertidal barnacle Semibalanus balanoides

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marien Ecology Progress Series 476 (2013): 141-151, doi:10.3354/meps10186.Gravid adults of the common intertidal barnacle Semibalanus balanoides (L.) brood fully developed larvae until individuals perceive some cue from the environment that triggers synchronous larval release. The prevailing hypothesis has been that phytoplankton blooms trigger release because they provide a food source for nauplius larvae. Through observations and field experiments, we tested the hypothesis that turbidity from any source, not just phytoplankton blooms, can trigger release. We documented five larval release events at three sites in the northeastern United States. Two events coincided with chlorophyll increases, and all five coincided with turbidity increases. In experiments, the larval release response was equivalent when adults were exposed to diatoms or inert synthetic beads, and it was significantly higher than under exposure to filtered seawater. We also tested the hypothesis that turbidity can decrease the risk of cannibalism for newly-released nauplii. Under experimentally manipulated conditions, adults consumed significantly fewer nauplii in a high-turbidity environment. We suggest that reproduction in this species may have evolved to coincide roughly with the local onset of winter/spring phytoplankton blooms, but the timing of larval release may have been fine-tuned further by cannibalism and predation pressures. The potential for turbid conditions to serve as a refuge for planktonic larvae of other marine organisms merits further investigation.Support for this work came from a National Science Foundation Graduate Research Fellowship and a student award from the Coastal Ocean Institute at Woods Hole Oceanographic Institution (both to JG)

Analysis of crowd behavior through pattern virtualization

The study of the concentration of individuals in public places such as squares, shopping malls, parks, gardens, etc., is an open study field in the different disciplines of science, that leads to the need of having systems that allow to forecast and to predict eventualities in uncontrolled situations, as it is the case of an earthquake. From that assumption, artificial intelligence, as a branch of computational sciences, studies the human behavior in a virtual way in order to obtain simulations based on social, psychological, neuro-scientific areas, among others, with the purpose of linking these theories to the area of artificial intelligence. This paper presents a way to generate virtual multitudes with heterogeneous behaviors, in such a way that the individuals that form the multitude present different behaviors

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)