Pier Pilings Research Articles

Medetomidine promotes settlement but inhibits recruitment of the introduced colonial ascidian (Botrylloides violaceus)

Colonial ascidians are common occupants of hard surfaces in coastal marinas as fouling organisms on pier pilings and ship hulls and have significant financial impact. Methods to inhibit fouling often are time consuming and labor intensive, thus treatments that prevent settlement for long time periods are warranted. Trybutyltin (TBT) appeared to be an effective antifouling agent, but is highly toxic to non-target species and now globally prohibited. Medetomidine is the active ingredient in the anti-fouling paint, Selektope, that shows promise to prevent attachment of marine fouling species. Here, we assessed the potential of medetomidine on larval metamorphosis of the invasive ascidian Botrylloides violaceus in static bioassays. We exposed newly released tadpole larvae to eight concentrations (0.5 mg/L, 1 mg/L, 5 mg/L, 10 mg/L, 20 mg/L, 40 mg/L, 50 mg/L) of medetomidine and recorded the number of larvae that were mobile, attached, metamorphosed or deceased after 1 h, 2 h, 4 h, 6 h, 24 h and 48 h. Larvae exposed to the highest concentrations of medetomidine quickly attached to the surface of Petri dishes, but failed to metamorphose. Larvae were mobile over the first 2 to 4 h of the experiment in the filtered sea water controls and low medetomidine concentrations. Larvae metamorphosed in all treatments except the two highest concentrations of medetomidine (40 and 50 mg/L), but ultimately all larvae exposed to medetomidine died. Medetomidine appears to have potential as a mechanism to control populations of B. violaceus, but we caution that further testing of non-target species is warranted.

Variations in benthic fluxes of sediments near pier pilings and natural rocky reefs

Marine artificial structures such as pilings are replacing natural habitats, and modifying surrounding areas, often resulting in local decreases in species diversity and facilitation of bioinvasion. Most research on the impacts of artificial structures in marine ecosystems has primarily focused on rocky bottom habitats and biodiversity, overlooking the effects of these structures on the functioning of nearby sedimentary habitats. Here we compared, for the first time, benthic metabolism (O2 fluxes) and sediment-water nutrient (inorganic nitrogen, phosphate, and dissolved organic nitrogen) fluxes in shallow water sediments adjacent to pilings and natural reefs. We also measured sediment properties (grain size, total organic carbon, total nitrogen, C:N ratio and chlorophyll-a content). We found that sediments near pilings were generally finer with greater C:N ratios than those near reefs, while differences in other sediment properties between types of habitats were dependent on the site. We found significant differences in the oxygen consumption, primary productivity, and net ecosystem metabolism in sediments around pilings compared to sediments near natural reefs, but these patterns differed by site. Net nutrient fluxes were similar in sediments near pilings and reefs at both sites. This study showed that although pilings can be associated with changes in the functioning of sedimentary habitats, patterns and the direction of change seem to vary depending on local conditions.

Rapid recovery of native habitat-builders following physical disturbance on pier pilings offsets colonization of cryptogenic and non-indigenous species in a Chilean port

Examining the effects of disturbances within marine urban communities can shed light on their assembly rules and invasion processes. The effects of physical disturbance, through the removal of dominant native habitat-builders, were investigated in the recolonization of disturbed patches and colonization of plates on pier pilings, in a Chilean port. On pilings, disturbance substantially affected community structure after 3 months, although it slowly converged across treatments after 10 months. On plates, cryptogenic and non-indigenous species richness increased with removal severity, which was not observed in natives. Opportunistic taxa took advantage of colonizing at an early successional stage, illustrating a competition-colonization trade-off, although indirect effects might be at play (e.g. trophic competition or selective predation). Recovery of the habitat-builders then occurred at the expense of cryptogenic and non-indigenous taxa. Whether natives could continue winning against increasing propagule and colonization pressures in marine urban habitats deserves further attention. The interactions between disturbance and biological invasions herein experimentally shown in situ contribute to our understanding of multiple changes imposed by marine urbanization in a growing propagule transport network.

A Cryptic Invasion in the Western Atlantic: Presence of the Fouling Barnacle Megabalanus zebra (Darwin, 1854) (Crustacea, Cirripedia) in the Caribbean Sea.

The barnacle Megabalanus zebra is largely known from ship hulls, with little information on its biology, ecology, and natural range. We identify M. zebra here from the southern Caribbean, based upon specimens collected as early as 2002. Challenges associated with identifying megabalinine species have delayed recognition of this species as distinct from other Caribbean Megabalanus. Sequenced material of M. zebra from Curaçao did not match M. zebra GenBank sequences that could be verified by descriptions or vouchered material. The presence of young M. zebra on vessels that have not left the Caribbean, as well as on pier pilings and resident buoys, indicate that this species is established in the tropical Western Atlantic Ocean, but the timing of its invasion remains unknown.

Invading the natural marine substrates: a case study with invertebrates in South Brazil

The number of biological invasions has grown dramatically in recent decades, as well as the world's human population and coastal development. Anthropogenic habitats, such as pier pilings and break waters, have been constantly added to marine environment, usually concentrated in estuarine areas. These habitats are focal points for marine invasions, but relatively little is known about the spread of non-indigenous species (NIS) to nearby natural habitats. This study aimed to determine the extent to which NIS have spread to natural substrates both inside estuarine areas and in the adjacent open sea. We conducted a field survey and a literature review, which have been critically discussed and validated. The updated NIS list of benthic invertebrates comprises 19 species: Ascidiacea (5), Cirripedia (5), Cnidaria (3), Mollusca (3), Polychaeta (1), Decapoda (1), and Echinodermata (1). Our results suggested substantial spread of non-indigenous species into natural substrates. Altogether, 18 and 16 NIS were recorded in artificial and natural substrata, both representing 13% of the total species in each habitat. The percentage of NIS was more pronounced in the estuarine areas, 17.6% in artificial habitats and 18.6% in natural ones. Programs developed for the monitoring of marine invasion have to broaden their focus including natural areas adjacent to ports and marinas, to follow the spread and impact of NIS on these areas.

The invasive worm Hydroides elegans (Polychaeta – Serpulidae) in southeastern Brazil and its potential to dominate hard substrata

ABSTRACTThe serpulid Hydroides elegans is recognized as an invasive species in many harbour areas of the world, growing mainly on man-made structures such as pier pilings, where native diversity is low. In addition, because they build large aggregations of calcareous tubes, this increases the maintenance and fuel costs of vessels. While H. elegans is well known for the North Atlantic, Europe, Caribbean and Pacific Ocean, detailed information of the species for the South Atlantic is missing. In the last decade, owners of boats moored at the Clube Naval Charitas (CNC), in the Guanabara Bay, southeastern Brazil noticed an increase in the occurrence of an encrusting organism that we identified as H. elegans. In this study we characterize H. elegans specimens from CNC and Itaguaí Harbor, both in southeastern Brazil, and discuss its distribution in the world. In addition, we deployed PVC panels at two different depths to quantify how H. elegans affects community assembling over two months. We observed that H. elegans could dominate hard substrata in the intertidal zone, occupying more than 50% of the available substrata. Considering the damage caused by H. elegans elsewhere and the ability of the species to monopolize space in the intertidal zone demonstrated here, accurate taxonomic information is essential for future monitoring and management of the species in Brazil and the South Atlantic.

Plasticity of Acquired Secondary Metabolites in Clathria prolifera (Demospongia: Poecilosclerida): Putative Photoprotective Role of Carotenoids in a Temperate Intertidal Sponge

Several marine sponges sequester high concentrations of carotenoids in their tissues. The diversity of carotenoid compounds has been described in detail for a handful of species, but to date, little attention has been paid to natural variability in the concentration and constituency of carotenoid pools. Also lacking are experimental tests of some of the proposed adaptive benefits of carotenoids to the sponge. To address some of these deficits in our understanding of sponge ecology, we used a combination of analytic chemistry, field surveys, and manipulative experiments to determine what function these compounds might play. Attention was focused on the common, carotenoid-rich intertidal sponge Clathria (Microciona) prolifera from Chesapeake Bay, Virginia, USA. Surveys of pier pilings indicated that C. prolifera was most common towards the surface of the water, with an average depth of 1 m, and also occurred most frequently on pilings exposed to sunlight. Total carotenoid concentrations (as estimated from spectroscopy) were maximal when solar radiation was nearing its northern maximum. However, HPLC analysis of crude acetone extracts highlighted several instances where concentrations of individual putative carotenoids were maximal during thermal (not solar) maxima in Chesapeake Bay. Naturally occurring sponges growing in environments protected from direct sunlight were found to have significantly lower total carotenoid concentration. In a manipulative field experiment, sponges transplanted from exposed habitats to shaded habitats showed significant decreases in carotenoid concentrations. HPLC analysis demonstrated that concentrations for several of the pigmented compounds decreased under reduced light levels. Given that sponges do not produce carotenoids de novo, the ecological role that these compounds play in sponge physiology deserves greater attention. Our findings indicate that solar radiation is an important factor in shaping carotenoid profiles of C. prolifera. While the physiological role and ultimate source of these compounds remains unclear, our data point to an adaptive function and indicate that C. prolifera is a useful species to address these questions.

Acoustic propagation in a shallow water duct with large obstructions.

The characteristics of shallow water harbor or mooring environments present unique challenges to an acoustic propagation modeler. Established acoustic propagation codes were developed to address problems in deep water or more open shallow water environments where spherical or cylindrical geometries and one‐way propagation approximations can easily be employed. In shallow harbors, large structures, including pier pilings and deep‐draft vessels, that represent a significant blockage of the water‐column propagation path may need to be accounted for. It is of interest to predict the received levels of the acoustic field transmitted past these obstructions. In order to more easily and accurately represent the complicated geometry of the boundary conditions encountered in this environment, a finite element model (COMSOL) is used. Using this model, predictions of the impact on low‐frequency acoustic propagation by structures typically encountered in a harbor are made.

An effect of pier pilings on nearshore submarine groundwater discharge from a (partially) confined aquifer

Concurrent bulk ground conductivity mapping and direct measurements of seepage rates were carried out near a pier at Shelter Island, New York, U.S.A. A shallow sediment layer was identified to provide confinement for lower aquifer units. The conductivity and seepage rate data indicate that pilings of the pier apparently pierce this shallow sediment layer, producing a comparatively high seepage rate driven by the hydraulic head of the (partially) confined aquifer, resulting in a substantial increase in submarine groundwater discharge (SGD) near the pier. Seepage rate measurements made close to the pier, which runs perpendicular to the shoreline, cannot be considered representative for the area. At the study site, the magnitude of SGD depends both on the distance from shore and on the distance from the pier, a rmding that confounds the commonly observed patterns of decreasing SGD with increasing distance from shore. This alteration of a groundwater flow pattern is a previously undescribed effect of anthropogenic perturbation in a coastal system.

The Colonisation of Human-made Structures by the Invasive Alga Codium fragile ssp. tomentosoides in the North Adriatic Sea (NE Mediterranean)

Human-made structures, such as groynes, breakwaters, seawalls, pier pilings and floating pontoons, are becoming common features of the landscape in urbanised coastal and estuarine areas. Despite this tendency few studies have focused on their ecology or on their potential impacts on natural assemblages of organisms. When artificial structures are introduced in areas with little or no hard substrata, they not only provide novel habitats, which enables the colonisation of sandy areas by hard-bottom dwelling species, but they can also provide suitable habitats for exotic species. Along the north-east coast of Italy, sandy shores are protected from erosion by a line of breakwaters, which runs almost uninterrupted for about 300 km. These structures provide habitat for a variety of macroalgae and invertebrates and also for the invasive green alga Codium fragile ssp. tomentosoides. The aim of this study was, therefore, to investigate patterns of distribution of this alga on breakwaters in Cesenatico. In particular, we compared the density of thalli, biomass, length and degree of branching of C. fragile ssp. tomentosoides between the landward and the seaward sides of breakwaters, to test the hypothesis that sheltered habitats (landward) represent more suitable habitats than exposed habitats (seaward). In general, the landward side of breakwaters supported greater numbers of thalli of C. fragile ssp. tomentosoides than seaward sides. Thalli grew longer and more branched in sheltered habitats, leading to an overall larger biomass of the alga on the landward side of breakwaters. The presence of sheltered human-made hard substrata in the vicinity of major trading ports and sources of eutrophication could enhance the dispersal of invasive species across regional and geographic scales. Thus, the effects of artificial structures and introduced species on coastal assemblages cannot be evaluated separately, but their synergistic nature should be considered in planning strategies for conservation of biodiversity in coastal habitats.

The introduction of artificial structures on marine soft- and hard-bottoms: ecological implications of epibiota

Artificial structures, such as seawalls, breakwaters, jetties, pontoons and pier pilings are becoming ubiquitous features of landscape in shallow coastal waters of urbanized areas. Nonetheless, few published studies have focused on their ecology and little effort has been devoted to determine how the various objectives (economic, social and ecological) involved in their introduction into natural systems can be reconciled.

Variable effects of larval size on post-metamorphic performance in the field

Larval quality may be capable of explaining much of the variation in the recruitment and subsequent population dynamics of benthic marine invertebrates. Whilst the effects of larval nutritional condition on adult performance have received the most attention, recent work has shown that larval size may also be an important and ubiquitous source of variation in larval quality. We examined the effects of variation in larval size on the post-metamorphic survival and growth of Watersipora subtorquata in 2 very different habitats - experimental substrata and pier pilings. We found strong effects of larval size on colony performance, although these varied among experiments. For colonies on experimental substrata, larval size positively affected adult survival and, initially, growth. However, after 3 wk in the field, there was no relationship between larval size and colony size, possibly because colonies were completely surrounded by newly settled organisms. Larval size also positively affected post-metamorphic growth of colonies on pier pilings, but, surprisingly, colonies that came from larger larvae had lower survival than colonies from smaller larvae. Overall, variation in larval size will strongly affect the recruitment and subsequent performance of adults in this species, although this may vary among different habitats. This study highlights the importance of examining the effects of larval quality on adult performance in as realistic conditions as possible, because of the strong interaction between larval size effects and the environment.

Abundance and colonization potential of artificial hard substrate-associated meiofauna

Meiofauna are known to live on hard substrates in association with periphytic and epiphytic algae and attached epibiota; however, the abundance, diversity and colonizing abilities of hard-substrate meiofauna have been poorly documented. We quantified meiofauna living on microalgal-covered pilings associated with a wood pier in a shallow (<2 m deep) estuarine embayment with the use of a suction sampler, and compared colonization of pier-piling and sediment-dwelling meiofauna onto collectors that capture suspended meiofauna from the water column. Collectors were small mesh pads (159 cm 3) suspended at mid-water depth, and their size and structural complexity were similar to floating or drifting masses of macroalgae that may be colonized by meiofauna. Sediment was collected by coring, and copepod (to species) and nematode (to genera) colonists on mesh pads were compared with pier-piling and sediment communities. Abundance of total meiofauna averaged 124±13.6 (S.E.) on pier pilings, compared to 2092±274.6 individuals 10 cm −2 in surrounding sediment. Phytal copepods (free-living copepods with prehensile first legs and dorsoventrally and laterally compressed body forms) and copepod nauplii dominated pier-piling collections, but nematodes were dominant on faunal collectors and in sediment. Phytal copepods also were abundant on faunal collectors but were rare in sediments. Copepod and nematode diversities were similar, but species composition was largely nonoverlapping, in pier pilings and sediments. Net recruitment of meiofauna to faunal collectors averaged about 900 individuals collector −1 day −1 during the 1-week experiment. Nematode and copepod colonists on faunal collectors were both much more similar to pier-piling than to sediment assemblages. These data suggest that meiofauna are abundant and diverse on algal-covered pier pilings, and they may become more important to marine ecology as artificial hard substrates increase with increasing urbanization. Furthermore, pier-piling meiofauna appear to readily migrate into the water column and probably contribute to a rapidly dispersing pool of meiofauna in estuaries.

Intertidal seawalls—new features of landscape in intertidal environments

Artificial structures, such as pier pilings, floating pontoons, breakwaters and seawalls are becoming common features of landscape in shallow coastal waters of urbanised areas, in some areas, replacing considerable portions of natural habitats. In Sydney Harbour (NSW, Australia), approximately 50% of the shore is composed of retaining seawalls or other built habitats. Intertidal seawalls and other similar structures provide new surfaces for colonisation by benthic organisms and therefore provide new intertidal habitats for estuarine animals and plants. They have the potential to supplement natural habitat by supporting natural assemblages, in terms of species composition and relative abundances. Alternatively, artificial structures may support only a subset of natural assemblages, provide habitat for additional species not found on nearby rocky shores, or provide habitat in which some species are consistently missing and additional species found (a combination of the previous two models). Understanding the ecological role that seawalls and other intertidal structures have in urbanised estuaries is important in planning of developments along foreshores. This study compared intertidal assemblages, at each of three different heights among seawalls and nearby horizontal and vertical rocky shores to specifically test the model that seawalls support the same assemblages of animals and plants as are found on natural rocky reefs. Hypotheses from this model were tested at three study locations by measuring abundances of animals and plants in quadrats in replicate sites on each structure. Results indicated that, at mid- and highshore levels, there were frequent differences between assemblages on natural shores and seawalls. In contrast, at lower levels, differences between assemblages on seawalls and vertical rocky reefs were small compared to differences between sites on each structure. Nevertheless, it appeared that the seawalls and rocky shores examined supported a similar suite of species and most differences were due to relative abundances and frequencies of occurrence of the species present. It is, however, premature to conclude that seawalls support similar assemblages to rocky shores until more intensive sampling has been done, specifically to search for rare species. In addition, until we have more knowledge on ecological processes in these assemblages, seawalls should not be considered as surrogates for natural shores.

Weak Effects of Epibiota on the Abundances of Fishes Associated with Pier Pilings in Sydney Harbour

Biogenic habitats have profound effects on the distribution and abundances of many organisms. Epibiota are major biogenic components of hard substrata in marine habitats, particularly on artificial structures such as pier pilings, and have the potential to influence organisms associated with these structures. This study tested hypotheses about effects of epibiota on abundances of fishes associated with pilings in Middle Harbour, Sydney. Amount of epibiota had no effect on abundances of most species of fish, suggesting that epibiota are not important resources for these species. Abundances of the hulafish, Trachinops taeniatus, were, however, found to be greater around pilings with large than pilings with small amounts of epibiota at one site, at each of two times. Experimental removals of epibiota from pilings were done to test the hypothesis that epibiota are an important resource to T. taeniatus. Despite great temporal fluctuations in abundances over the duration of the experiment, the response of T. taeniatus to the removal of epibiota from pilings was as predicted, falling to zero following removal of epibiota. Although this suggests that epibiota are an important resource for this species, this pattern was spatially and temporally variable. We suggest that variation in the amount of epibiota has minor effects on the abundances of fishes around pilings.

Wave Energy and Direction Observed near a Pier

Alongshore gradients in wave energy and propagation direction were observed near a pier that extends 500 m from the Duck, N.C., shoreline to about 6-m water depth. When incident waves approached the beach obliquely, wave energy observed near the shoreline 200 m downwave of the pier was as much as 50% lower than observed 400 m downwave, and waves close to the pier were more normally incident than those farther downwave. Alongshore gradients were much smaller 400 m offshore of the shoreline, upwave of the pier, and with nearly normally incident waves, confirming that the gradients are associated with wave propagation under the pier. A spectral refraction model for waves propagating over the measured bathymetry, which includes a depression under the pier, accurately predicts the observations 400 m downwave of the pier, but overpredicts energy near the pier. Refraction model predictions that include partial absorption of wave energy by the pier pilings reproduce the observed alongshore gradients, suggesting that piling-induced dissipation may be important.

Effects of shading on subtidal epibiotic assemblages

Mensurative and manipulative experiments were done to test hypotheses about the effects of shading on subtidal assemblages of epibiota. Previous studies found large differences in the composition of epibiotic assemblages on pier pilings (shaded by boats and wharves) and adjacent rocky reefs at marinas in Sydney, Australia. Different degrees of shading were proposed to explain the differences between assemblages on these two substrata. Assemblages of epibiota on free-standing, unshaded pilings were sampled and, as predicted, found to be different from those on shaded pilings and similar to those previously described on rocky reefs. Unshaded pilings were covered primarily by filamentous and foliose algae and spirorbid polychaetes. Patches on these unshaded pilings were then experimentally shaded to test the hypothesis that increased shading would result in the assemblages changing to become like those on permanently shaded pilings. After shading patches for 9 months, the composition of assemblages changed compared to controls and taxa such as bryozoans ( Fenestrulina mutabilis), serpulid polychaetes, solitary ascidians ( Styela plicata) and sponges became common. Results suggested that different degrees of shading could explain differences in the cover of many epibiota growing on pier pilings and adjacent rocky reefs at marinas. Other factors that may be important in structuring subtidal epibiotic assemblages are also discussed.

Differences Between Subtidal Epibiota on Pier Pilings and Rocky Reefs at Marinas in Sydney, Australia

Epibiotic assemblages growing subtidally on pier pilings and on vertical surfaces of adjacent rocky reefs were sampled twice at a number of marinas around Sydney, Australia. As predicted, the assemblages on pilings and nearby rocks were quite distinct. Furthermore, relative differences between the two surfaces were remarkably consistent among locations and through time, despite the fact that the exact compositions of these assemblages differed among marinas. Assemblages on pilings were typically dominated by species of encrusting bryozoans, serpulid polychaetes, sponges and ascidians. The most common taxa on rocks were spirorbid polychaetes and filamentous and foliose algae. No one taxon was peculiar to either rocks or pilings; rather, each was found in very different proportions on the two surfaces. The results suggest that pilings at marinas are creating a habitat very different from the primary natural hard substratum (sandstone rocky reef) in these areas. Possible reasons and consequences for the differences between epibiota on pilings and rocks are discussed.

Interactive effects of shading and proximity to the seafloor on the development of subtidal epibiotic assemblages

A manipulative experiment was done to test hypotheses about the interactive effects of shading and proximity to the seafloor on the development of subtidal epibiotic assemblages. It was proposed that differences in these 2 factors could explain differences described previously between assemblages of sessile organisms on rocky reefs and pier pilings in estuaries. Sandstone settlement plates were deployed in 2 positions (close to and far from the seafloor) and sets of plates were experimentally shaded in each position. Effects of shading and proximity to the seafloor were apparent after 12 wk and many persisted for all 33 wk of the experiment. Largest differences in assemblages were due to position relative to the seafloor (which greatly affected the cover of spirorbid polychaetes, barnacles, bryozoans and sponges) and there was a significant multivariate effect of shading on assemblages close to the seafloor. Shading influenced the cover of colonial ascidians, algae and cyanobacteria in both positions, but many other taxa in only 1 position. Possible reasons for these differences are discussed. Results suggested that differences in assemblages between rocky reefs and pilings could largely be due to differences in shading and proximity to the seafloor.

Two levels of spacing and limits to local population density for settled larvae of the ascidian Clavelina moluccensis: a nearest-neighbour analysis

Among sessile marine invertebrates, the dispersion patterns of settling larvae are likely to strongly affect the nature and strength of subsequent intraspecific interactions. We use a recently developed graphical analysis technique to examine in situ spacing among settled larvae of the colonial ascidian Clavelina moluccensis. Larvae were mapped at settlement each day for 1 month at the time of their release from adults. Experimental plots measuring 90×90 mm were located on naturally occurring bare patches of wood on pier pilings which were extensively encrusted with sponges and ascidians. An inclusive one-tailed nearest-neighbour analysis applied at the time of the maximum number of individuals per plot revealed consistent fine-scale regular spacing between settled larvae. Furthermore, a two-tailed goodness-of-fit analysis indicated two modes of spacing: one at about 4.5 mm and the other at around 9 mm. No contact between larvae was observed at settlement and the spatial regularity is interpreted as a response of settling larvae to water-borne cues released from settled individuals. The two modes of spacing indicate the possibility of kin recognition as has been demonstrated for bryozoans. Water-borne cues may also limit local population density, as those plots with a high density of settlers showed a much greater decrease in settlement rate over time than low-density plots. Our findings are consistent with the hypothesis that intraspecific competitive interactions shape the patterns of dispersion of these invertebrates on hard substrata in the field.