Natural Seagrass Beds Research Articles

Behavioral hotspots of bottlenose dolphins in industrialized ship channels

Anthropogenic activity in coastal areas can damage marine habitats and alter marine mammal behavior and habitat use. Understanding behavioral associations with diverse habitat features in industrialized coastal areas is crucial for marine mammal conservation management. A shore-based digital theodolite was used to assess the behavioral states and habitat use of common bottlenose dolphins (Tursiops truncatus) off Port Aransas, Texas across seasons. The relationship between behavioral states and environmental and geographical variables were analyzed. Behavioral hotspots were identified. Dolphins frequently foraged (46%), indicating the area is an important feeding ground. Dolphins also traveled (25%) and milled (22%), with less frequent occurrences of socializing (6%) and resting (1% of observations). Season, time of day, and distance to shoreline were significant predictors of foraging and traveling behavioral states. Dolphins engaged in all behavioral states closer to seawall shorelines than to mangroves and natural seagrass beds, suggesting that hard shoreline features may influence daily activity patterns. Despite daily anthropogenic operations, bottlenose dolphins use features of the industrialized area (i.e., deeply dredged channels, human-engineered seawalls) to engage in a variety of behaviors. Monitoring of dolphin behavioral states and habitat use in active ship channels are needed to assess changes from baseline data from increasing coastal development and vessel activities.

Restored seagrass beds support Macroalgae and Sea Urchin communities

Seagrass decline and loss have been reported worldwide. Restoration is an increasingly popular approach to improving ecosystem services and may become a mitigation measure for seagrass habitat loss. However, in Indonesia seagrass restoration is still at a trial stage and small scale. This study aimed to compare the seaweeds and sea urchin communities in restored seagrass beds and in control areas (natural seagrass beds) around Barrang Lompo Island, Indonesia. Sea urchin and seaweed community structure was compared using non-metric multidimensional scaling and Bray-Curtis cluster analysis, while (as an indicator of ecosystem service provision) species contribution to the difference in sea urchin and seaweed community structure was analysed using SIMPER (similarity of percentages); both analyses were implemented in PRIMER v7. Regression analysis in SPSS v25 was applied to evaluate the correlations between sea urchin and seaweed density, sea urchin and seagrass density, seaweed and seagrass density. The results indicate that, although the ability to harbour associated organisms differed, restored seagrass beds can provide habitat for associated organisms and improve ecosystem services.

Assessment of restoration success in a transplanted seagrass bed based on isotopic niche metrics

A major highlight of restoration efforts is to improve the ecological structure and function of the natural ecosystem in the restored habitat. Assessment of restoration success is a crucial component of an optimal ecological management strategy. In studies to determine the restoration success of a transplanted seagrass habitat by assessing trophic recovery, we examined carbon and nitrogen stable isotope ratios of organic matter sources and macrobenthic assemblages in a transplanted eelgrass Zostera marina bed. The eelgrass bed was restored about 2 years after transplantation in a southern coastal bay of Korea, and consequently, the food web structure in the bed was compared with that in a natural reference site. Our results revealed no significant differences in isotopic values of both macrobenthic consumers and their putative food sources between the transplanted and natural seagrass beds. These isotopic similarities in florae and faunae in the two beds suggest a uniformity in food web structure formed by the diversity and availability of resources, and thereby suggest similarities in the resource–consumer relationship. Isotopic niche indices and high dietary overlaps of feeding guilds in the transplanted and natural beds further suggest the transplanted habitat provides similar ecological functions and ecosystem services to its natural counterpart. Collectively, our results suggest the eelgrass transplantation led to successful restoration of a common seagrass bed, with recovery of the functional properties of the food web structure. Finally, our findings support the idea that stable isotope measures can provide a better understanding of the functioning of restored ecosystems, and improve post-transplantation monitoring efforts for the future planning and managing of successful habitat restoration.

Macrozoobenthos community structure in restored seagrass, natural seagrass and seagrassless areas around Badi Island, Indonesia

Seagrass ecosystems play an important role in providing food and protection to the organisms that live in and around seagrass meadows. However, due to heavy pressure from human activities, many seagrass beds have been degraded, with the loss or reduction of important ecological functions. Therefore, seagrass restoration needs to pay attention to the recovery of these ecological functions. This study aimed to determine the success of the seagrass restoration activities around Badi Island, South Sulawesi, Indonesia, in supporting the recovery of ecological functions, as viewed from the macrozoobenthos community structure. Data on macrozoobenthos community structure in transplanted seagrass areas was compared with the macrozoobentos community structure of nearby natural seagrass beds and seagrassless areas. The macrozoobenthos identified comprised 34 species from 3 classes in the seagrass restoration area, 73 species from 9 classes in natural seagrass beds, and 24 species from 4 classes in areas without seagrass. A one way ANOVA test indicated significant differences in macrozoobenthos density between the transplanted areas and natural seagrass beds but not sites without seagrass. Ecological indicators such as the diversity index and evenness index showed a higher level of macrozoobenthos community structure in all the sampling sites. We conclude that, as transplanted seagrasses become established, they can provide ecological functions and serve as habitat for a wider variety of other organisms, as reflected in the community structure of the associated macrozoobenthic organisms.

Physical structure of artificial seagrass affects macrozoobenthic community recruitment

Seagrass ecosystems are important in supporting marine biodiversity. However, the worldwide decline in seagrass areas due to anthropogenic factors leads to a decrease in the marine biodiversity they can support. There is growing awareness of the need for concepts to conserve and/or rehabilitate seagrass ecosystems. One option is to create artificial seagrass to provide a physical structure for the marine organisms to colonize. The objective of this research was to analyze the effect of some artificial seagrasses and seagrass transplants on marine biodiversity, with a focus on the macrozoobenthic community. The experimental design compared two types of artificial seagrass (polypropylene ribbons and shrub-shaped plastic leaves), and seagrass transplants from nearby seagrass meadows. The experimental plots were 4 x 4 m2 with 3 replicates. Macrozoobenthic communities were sampled fortnightly for 3.5 months. At the end of the experiment, makrozoobenthos were also sampled from a natural seagrass bed nearby. Of 116 macrozoobenthic species in the artificial seagrass plots, 91 were gastropods. The density of the macrobenthic fauna increased from the beginning to the end of the study in all treatments, but the increase was only significant for the artificial seagrass treatment (i.e. shrub-like plastic leaves). There was a distinct separation between the macrozoobenthic community structure found in the restoration plots (artificial seagrass and transplanted seagrass) compared to natural seagrass beds.

Particle trapping and retention by Zostera noltii: A flume and field study

The relative particle trapping ability of Zostera noltii Hornem. was examined in an 8m seawater flume. Two size classes of fluorescent tracer particles (150–250μm and <63μm) were used to determine the number of particles captured by bare sediment (control) and three densities of Z. noltii (200, 600 and 1000shootsm−2) at three flow velocities (0.04, 0.15 and 0.4ms−1). Particle sizes, plant densities and flow velocities were all within the range of conditions observed in the field. Fewer large particles were trapped at higher flow rates (ANOVA, F2,30=23.29, p<0.001, n=36), with the mean number of particles decreasing with increasing flow. The numbers of large particles trapped in both low and medium flows were similar in vegetated and bare sediments, suggesting that particles were deposited due to low energy conditions rather than due to the presence of vegetation. At low flow, low density seagrass beds trapped more particles of both sizes on the sediment surface than higher density beds. This result was explained in hydrodynamic terms because skimming flow develops at higher shoot densities, carrying suspended particles over the plants following leaf reconfiguration in flow. This work was extended to the field and sediment retention in high density Z. noltii (Tay Estuary, Scotland, U.K.) was compared to bare sediment over one week (14 tides). Tracer particles were added directly among natural seagrass beds exposed at low tide. After large losses due to initial particle resuspension, Z. noltii retained large particles (150–250μm) more effectively than bare plots over time. Particle retention for small particles (<63μm) was similar for both plot types. Mechanisms underlying the results are suggested and the findings discussed.

Evaluation of Seagrass Planting and Monitoring Techniques: Implications for Assessing Restoration Success and Habitat Equivalency

Abstract Restoration has become an integral part of coastal management as a result of seagrass habitat loss. We studied restoration of the seagrass (Halodule wrightii) near Tampa Bay, Florida. Experimental plots were established in June 2002 using four planting methods: three manually planted and one mechanically transplanted by boat. Seagrass cover was recorded at high resolution (meter scale) annually through July 2005. Natural seagrass beds were concurrently examined as reference sites. We also evaluated the suitability of a commonly used protocol (Braun‐Blanquet scores, BB) for comparing the development of seagrass cover using the planting methods and quantifying spatial patterns of cover over time. Results show that BB scores mirrored conventional measures of seagrass characteristics (i.e., shoot counts and above‐ and belowground biomass) well when BB scores were either low or very high. However, more caution may be required at intermediate cover scores as judged by comparison of BB scores with direct measurement of seagrass abundance. Significant differences in seagrass cover were detected among planting methods and over time (2002–2005), with manual planting of rubber band units resulting in the highest cover. In contrast, the peat pot and mechanical planting methods developed very low cover. Recovery rates calculated from development of seagrass spatial cover were less than those reported for natural expansion. Importantly, time to baseline recovery may be substantially greater than 3 years and beyond standard monitoring timelines. Prolonged recovery suggests that the rate of service returns, critical for estimating compensatory restoration goals under habitat equivalency analysis, may be severely underestimated.

Application of an ecosystem model for the environmental assessment of the reclamation and mitigation plans for seagrass beds in Atsumi Bay

An ecosystem model was used to evaluate the effects of reclaiming seagrass beds and creating artificial shallows with seagrass beds to mitigate the effects of the reclamation. The applied model can simulate the pelagic and benthic ecosystems including seagrass beds and tidal flats. The objectives of this study were (a) to investigate the likelihood of cultivating and maintaining seagrass beds in artificial shallows (Part 1), and (b) to understand the effects of the reclamation of seagrass beds and the creation of artificial shallows on the water quality in the estuary (Part 2). In Part 1, first, the nutrient turnover rates due to both biochemical and physical processes in the natural seagrass beds where reclamation is proposed were analyzed. Biological processes rather than physical processes were the most significant driving forces of nutrient cycles in seagrass beds. Second, the effects of filter feeding benthic fauna (suspension feeders) in the seagrass beds were analyzed. The scenario with suspension feeders resulted in higher transparency of the water column (8.7% decrease in the light attenuation coefficient) and an increase in nutrient supply (24.9% increase in NH 4-N in the water column) contributing to the high specific growth rate of seagrass. Third, the specific growth rate of seagrass on the proposed artificial shallows was measured. The value on the artificial shallows set at a depth of datum line minus 0.8 m (D.L. − 0.8 m) was approximately the same as that of the natural seagrass beds. In Part 2, first, water quality in the estuary was compared among the scenarios with/without natural seagrass beds and artificial shallows. Then, the defined values of the water purification capability of (a) artificial shallows with/without seagrass beds, and (b) natural seagrass beds per unit area were evaluated. The reclamation of the natural seagrass beds resulted in a decrease of the removal of phytoplankton and detritus from the pelagic system (i.e. resulted in a loss in the purification rate). In contrast, the creation of artificial shallows resulted in an increase of the removal of phytoplankton and detritus from the pelagic system (i.e. resulted in a gain in the purification rate). Based on an annual average, approximately twice as much phytoplankton was removed from the artificial shallows at the depth D.L. − 0.8 m, than at the depth, D.L. − 1.5 m, and the artificial shallows with seagrass beds removed pelagic DIN and DIP at a rate 120% higher than that without seagrass beds.

Edge effects and patch size in seagrass landscapes: an experimental test using fish

Edge effects and bed size are 2 main landscape-scale parameters that may affect fish in seagrass. We tested their influence on the species richness per unit area and density of fish in 6 Zostera capricorni seagrass beds ranging in size from 2300 to 211 200 m 2 , in the Pittwater estuary, NSW, Australia. The effect of edge interacted with bed size. The species richness was lower in edge than inner regions of the larger beds, but did not differ between regions in smaller beds, in which the species richness was similar to the inner regions of large beds. The density of fish (all species combined) varied with bed size in 1 of the 2 seasons sampled, but not with region. The densities of some individual species were lower in the larger beds compared to smaller beds (5 species), while others were greater (3 species), although for some species this was inconsistent between seasons. We then tested whether species richness and abundance were responding to patch area, perimeter, or perimeter: area ratio (P:A ratio) using artificial seagrass units (ASUs) of different shapes and sizes. All ASU designs had similar total abundances of fish species (per ASU), yet 1 design was smaller in area, so these smaller ASUs had greater species richness per unit area. The ASUs were smaller than the natural seagrass beds, and it seems that, although edge effects appeared in large natural seagrass beds, in smaller patches the total area rather than amount of edge influenced the species richness.

Comparison of restored and natural seagrass beds near Corpus Christi, Texas

Structural equivalence between seagrass restoration sites and adjacent natural seagrass beds on the mid Texas coast was assessed six times between April 1995 and May 1997. Throw traps and corers were used for quantitative sampling. Restoration sites were 2.7 to 6.6 yr old when first sampled and 3.7 to 8.2 yr old when last sampled. There were few significant differences in water column, seagrass, or sediment characteristics, in fish and decapod (nekton) densities, or in nekton and benthos community compositions between restored and natural seagrass habitats at any time during the study period. Differences in densities of dominant benthic invertebrates were regularly observed, with greater densities of more taxa observed in natural seagrasses than in restored beds. Densities of Class Oligochaeta and the polychaetePrionospio heterobranchiata are proposed as potential indicators of structural equivalence in restored seagrasses. This study indicates that seagrass restorations in the vicinity of Corpus Christi, Texas, exhibit minimal quantitative differences in community structure (except for benthos) relative to adjacent natural seagrass beds after 3 to 5 yr.

Fauna of Natural Seagrass and TransplantedHalodule wrightii(Shoalgrass) Beds in Galveston Bay, Texas

AbstractWe compared nekton and benthos densities and community compositions in a natural mixed seagrass bed dominated byHalodule wrightii(shoalgrass) with those found in three shoalgrass transplant sites and adjoining sand habitats in western Galveston Bay, Texas, U.S.A. Quantitative drop traps and cores were used to compare communities up to seven times over 36 months post‐transplant where transplant beds survived. Total densities of fishes, decapods, annelids, benthic crustaceans, and most dominant species were significantly higher in natural seagrass than in transplanted shoalgrass or sand habitats during most sampling periods. On occasion, fish and decapod densities were significantly higher in transplanted shoalgrass than in adjoining sand habitats. No consistent faunal differences were found among transplant sites before two of three sites failed. Taxonomic comparison of community compositions indicated that nekton and benthos communities in natural seagrass beds were usually distinct from those in transplanted beds or sand habitats, which were similar. We conclude that reestablishing a shoalgrass bed that resembles a natural seagrass bed and its faunal communities in the Galveston Bay system will take longer than 3 years, provided that transplants persist.

Settlement and Density of Juvenile Fish Assemblages in Natural, Zostera Capricorni (Zosteraceae) and Artificial Seagrass Beds

Few studies have validated the use of artificial seagrass to study processes structuring faunal assemblages by comparison with natural seagrass. One metric (fish recruitment) for evaluating the use of artificial seagrass was used in the present study. Settlement and recruitment of juvenile fish was estimated in natural, Zostera capricorni Aschers, and artificial seagrass in Botany Bay, NSW, over 6 consecutive days. Tarwhine, Rhabdosargus sarba, dominated the catch from both habitats, and there was no significant difference in abundance of recruits among the habitats. This was at least partly caused by large spatial and temporal variation in abundance. Daily abundances of R. sarba recruits suggested movement between seagrass beds, but could not be confirmed without tagging individual fish. Rhabdosargus sarba settlers were less abundant than recruits, but were also patchily distributed amongst natural and artificial seagrass beds. Most other species were also found in similar abundance in the two habitats, except stripey, Microcanthus strigatus, which was more abundant in artificial seagrass. Overall, fish assemblages in natural and artificial seagrass were similar. Artificial seagrass may therefore be useful for monitoring settlement and recruitment of juvenile fishes to disturbed habitats, to predict the success of habitat remediation. However, if artificial seagrass is used to model processes occurring in natural seagrass, it is necessary to consider species-specific responses to the artificial habitat.

Response of bay scallops to spawner transplants:a test of recruitment limitation

Response of bay scallops to spawner transplants:a test of recruitment limitation

Production in Natural and Restored Seagrasses: A Case Study of a Macrobenthic Polychaete.

Restoration of seagrass beds has been suggested as a method to correct declining vegetation cover in shallow waters. Secondary production of the polychaete Kinbergonuphis simoni was used to evaluate faunal equivalency of newly restored (2-yr-old) seagrass beds to beds that are mature (at least 17 yr old) in an embayment in Tampa Bay, Florida. Information on density of polychaetes, size structure, reproductive characteristics, and production (growth increment summation method) was collected from May 1989 to February 1991 from individuals within monthly sediment cores from both planted and natural seagrass beds. Additionally, total macroinfauna were sampled every 3 mo at the same sites. Deposit-feeding polychaetes were the dominant macroinfaunal taxa in all seagrass beds examined. Three polychaete species, including Kinbergonuphis simoni, displayed significantly enhanced abundances in planted compared to natural seagrass beds. Population abundance and size class distribution of Kinbergonuphis within planted sites displayed more rapid and consistent population increases after populations disappeared in winter 1989 than that recorded for natural sites. Production values of planted areas over 22 mo were an order of magnitude higher than that recorded in natural areas. Higher production values resulted principally from rapid recovery of populations in planted areas in contrast to natural beds, which did not display such resiliency. Biomass allocation to reproduction did not vary among individuals from natural and planted beds, but more total individuals were participating in reproductive events in planted areas. Results of this study suggest that in addition to abundance of some frequently encountered deposit-feeders, functional characteristics of a common polychaete from seagrass beds vary with age of bed. Moreover, the link between faunal functional equivalency and vegetational cover remains obscure.

Phenology and reproductive physiology of Thalassia testudinium from the Western tropical Atlantic

Phenological investigations in natural seagrass beds of Texas, Florida and St. Croix, U.S. Virgin Islands, and reproductive physiology studies under controlled conditions suggest that flowering in Thalassia testudinum Banks ex König is related to the temperature progressions that follow winter minima. Phenological analyses did not show significant site differences that were related to latitude for any of five phenophases, but indicated that flowering may be nearly synchronous in Texas, Florida and St. Croix. Statistical analyses of one phenophase, the initial appearance of visible floral buds, and the temperatures antecedent to this phenophase indicated that flowering in St. Croix is preceded by a significantly higher temperature progression than that in Florida or in Texas. Under controlled conditions, plants of Texas were induced to flower at temperatures at or below 23°C and to reach anthesis at 23°C, but plants of more tropical origin, St. Croix and Mexico, flowered less frequently and at a slightly higher temperature, 24–26°C. Plants of diverse origin produced flowers under continuous light, suggesting that photoperiod does not play a significant role in flowering phenology. The combined studies in the natural seagrass beds and in the laboratory under controlled conditions indicate that temperature responses for St. Croix plants are probably genotypically different from those of Florida and Texas.

REPRODUCTIVE PHYSIOLOGY IN THE SEAGRASS, SYRINGODIUM FILIFORME, FROM THE GULF OF MEXICO AND THE CARIBBEAN

Reproductive physiology in Syringodium filiforme Kütz. is controlled primarily by temperature under day lengths ranging from 12 hr to continuous light. Texas plants can be induced to flower at temperatures ranging from 20 to 24 C, but southern Gulf of Mexico and Caribbean plants are most readily induced at 23–24 C. Texas plants proceed to anthesis at temperatures above 22 C, but St. Croix plants require higher temperatures, above 25 C, for emergence of flowers from the bracts. Flowers induced under continuous light proceed to anthesis under day lengths shortened to 11 hr, but further floral induction is inhibited even under inductive temperatures. In natural seagrass beds, flowering occurs primarily under lengthening day lengths and warming temperatures that follow winter minima, but inflorescences may occur at other times of the year if temperatures permit.

Reproductive Physiology in the Seagrass, Syringodium filiforme, from the Gulf of Mexico and the Caribbean

Reproductive physiology in Syringodium filiforme Kütz. is controlled primarily by temperature under day lengths ranging from 12 hr to continuous light. Texas plants can be induced to flower at temperatures ranging from 20 to 24 C, but southern Gulf of Mexico and Caribbean plants are most readily induced at 23–24 C. Texas plants proceed to anthesis at temperatures above 22 C, but St. Croix plants require higher temperatures, above 25 C, for emergence of flowers from the bracts. Flowers induced under continuous light proceed to anthesis under day lengths shortened to 11 hr, but further floral induction is inhibited even under inductive temperatures. In natural seagrass beds, flowering occurs primarily under lengthening day lengths and warming temperatures that follow winter minima, but inflorescences may occur at other times of the year if temperatures permit.

Flowering under controlled conditions by Cymodocea rotundata from the Palau Islands, Micronesia

Flowering of Cymodocea rotundata Ehrenb. & Hempr. ex Aschers. has been reported in natural seagrass beds only in 1871 and 1967. The production of staminate flowers on three separate occasions in 1977–1978 in experimental cultures transplanted from Kayangel Atoll suggests primarily temperature control.