Larval and juvenile fishes occurring with flood tides on an intertidal mudflat in the Tama River estuary, central Japan

Intertidal movements of fish larvae and juveniles on a mudflat in the Tama River estuary, central Japan, were investigated by comparing the abundance and sizes of fishes caught in the intertidal zone during flood tides with those in the subtidal zone during low tides. A total of 28465 individuals, belonging to 9 families and 20 species, were collected by small purse seine. Among the abundant species, planktonic larvae and juveniles of gobiids and Konosirus punctatus were more abundant in the intertidal zone at flood tide than the subtidal zone at low tide. Similar occurrence patterns were found in juvenile Plecoglossus altivelis altivelis and Lateolabrax japonicus, having fully developed swimming abilities. In contrast to these species, much higher abundances of epibenthic juveniles of 2 gobiids (Acanthogobius flavimanus and Gymnogobius macrognathos) were found in the subtidal zone at low tide, although they also utilized the intertidal zone at flood tide.     

长江口潮间带底栖生物生态及变化趋势

基于长江口3个区域潮间带(崇明东滩、南汇边滩和嵊山岛)监测数据,对长江口区域潮间带底栖生物生态现状及变化趋势进行评价。结果表明,2019年长江口海域泥相和岩相潮间带共鉴定大型底栖生物9门57种,软体动物、甲壳类和多毛类构成主要类群。崇明东滩、南汇边滩两个泥相潮间带底栖生物平均栖息密度分别为96.4个/m~2和160.4个/m~2,平均生物量分别为68.42 g/m~2和45.71 g/m~2;嵊山岛岩相潮间带平均栖息密度和生物量分别为488.9个/m~2和763.72 g/m~2。各断面多样性、丰富度和均匀度指数分别位于1.36—3.24、0.75—2.88和0.48—0.77,泥相潮间带低潮区生物多样性优于中潮区和高潮区,岩相潮间带中潮区生物多样性最好。聚类分析可见长江口海域潮间带底栖生物分为泥相和岩相2个大组群,物种分布存在明显的分潮区现象,高潮区站位成群或与个别中潮区站位成群,低潮区站位成群或与个别中潮区站位成群,表明底质类型和潮汐是影响潮间带大型底栖生物群落结构的主要因子。近30年来,崇明东滩和南汇边滩底栖生物种类数存在一定波动,嵊山后陀湾断面生物种类数明显下降;3个区域潮间带...     

UK intertidal foraminiferal distributions: implications for sea-level studies

Foraminiferal assemblages have been collected from ten intertidal study areas situated on the east, south and west coasts of the UK. The assemblages display a vertical zonation which indicates that the distribution of foraminifera in these intertidal environments is usually the direct function of altitude with the duration and frequency of intertidal exposure the most important factors. Multivariate analyses separate foraminiferal assemblages into two faunal zones: a high- and middle marsh zone consisting of differing abundances of Jadammina macrescens, Trochammina inflata and Miliammina fusca; and a low-marsh and tidal flat zone dominated by calcareous foraminiferal species, notably Elphidium williamsoni, Haynesina germanica and Quinqueloculina spp. These faunal zones are similar to those in other mid-latitude, cool temperate intertidal environments although there are spatial and temporal variations between areas. The altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level.     

Nitrate uptake varies with tide height and nutrient availability in the intertidal seaweed Fucus vesiculosus

Intertidal seaweeds must cope with a suite of stressors imposed by aerial exposure at low tide, including nutrient limitation due to emersion. Seaweeds can access nutrients only when submerged, so individuals living higher compared to lower on the shore may have adaptations allowing them to acquire sufficient amounts of nutrients to survive and maintain growth. Using a combination of observations and experiments, we aimed to identify intraspecific variation in nitrate uptake rates across the intertidal distribution of F. vesiculosus, as well as test for acclimation in response to a change in tide height. We replicated our study at sites spanning nearly the entire Gulf of Maine coastline, to examine how local environmental variability may alter intraspecific variation in nitrate uptake. We found that average nitrate uptake rates were ~18% higher in upper compared to lower intertidal Fucus vesiculosus. Furthermore, we found evidence for both acclimation and adaptation to tide height during a transplant experiment. F. vesiculosus transplanted from the lower to the upper intertidal zone was characterized by increased nitrate uptake, but individuals transplanted from the upper to the lower intertidal zone retained high uptake rates. Our observations differed among Gulf of Maine regions and among time points of our study. Importantly, these differences may reflect associations between nitrate uptake rates and abiotic environmental conditions and seaweed nutrient status. Our study highlights the importance of long‐term variation in ambient nutrient supply in driving intraspecific variation of seaweeds across the intertidal gradient and local and seasonal variation in ambient nutrient levels in mediating intraspecific differences.     

Spatial distribution and quantification of Fucus species and Ascophyllum nodosum beds in intertidal zones using spot imagery

Low tide SPOT images were selected from two French coast areas characterized by important Fucaceae populations (Pleubian-Bréhat site in Northern Brittany and Ré Island on the Atlantic coast).A specific data transformation yielding the theoretical algal cover was used. This index takes the radiometric properties of the intertidal zone and of the Fucaceae into account. Satellite data cover was validated by comparing it with selected field samples.Other field data indicate that a linear relation exists between cover and biomass. This relationship is quite independent of cover patchiness. However, it can vary according to species, season and location. Hence it was possible to estimate Fucus sp and Ascophyllum nodosum harvestable biomass using appropriate segments of the intertidal zone.     

Activity rhythms and cyclical changes of microhabitat preferences in the intertidal pipefish Nerophis lumbriciformis (Pisces: Syngnathidae)

As an inhabitant of the intertidal zone, Nerophis lumbriciformis predictably should show a clear rhythmic activity, with its maximum closely correlated with the high tide period, as observed in several other rocky intertidal fish species. We investigated the rhythmic activity patterns of N. lumbriciformis and analysed to what extent specific substratum preferences may be linked to water level and, ultimately, to the particular activity rhythm patterns of the fish. To determine N. lumbriciformis substratum preferences, two different experiments were conducted. The first evaluated substratum preferences from among a group of the four most common substrates found in the sample area. The second experiment evaluated the fish's maintenance of that substratum preference, after alteration of the water level in a simulated ebb tide. From the available substrata, N. lumbriciformis displayed a clear preference for algae until the water level began to decrease. Then, the preference radically shifted from algae to boulders. N. lumbriciformis showed a clear rhythmic activity, affected by both tidal and circadian periodicity, producing asymmetrical activity peaks. Unlike the rhythms of other rocky intertidal fish species, the maximum activity peaks were not centred at the expected high tide period. The adaptive explanation for the apparently peculiar activity peaks appears to be related to the particular substratum preferences of N. lumbriciformis. The detected circatidal period seems, consequently, closely related to small migrations between substrata, whilst the observed increase in diurnal activity, independent of the tidal cycle, may be related to predatory activity, since N. lumbriciformis is a visual feeder. Electronic Publication     

INVERTEBRATE‐MEDIATED NUTRIENT LOADING INCREASES GROWTH OF AN INTERTIDAL MACROALGA1

Even in nitrogen‐replete ecosystems, microhabitats exist where local‐scale nutrient limitation occurs. For example, coastal waters of the northeastern Pacific Ocean are characterized by high nitrate concentrations associated with upwelling. However, macroalgae living in high‐zone tide pools on adjacent rocky shores are isolated from this upwelled nitrate for extended periods of time, leading to nutrient limitation. When high‐intertidal pools are isolated during low tide, invertebrate‐excreted ammonium accumulates, providing a potential nitrogen source for macroalgae. I quantified the influence of mussels (Mytilus californianus Conrad) on ammonium accumulation rates in tide pools. I then evaluated the effects of ammonium loading by mussels on nitrogen assimilation and growth rates of Odonthalia floccosa (Esp.) Falkenb., a common red algal inhabitant of pools on northeastern Pacific rocky shores. Odonthalia was grown in artificial tide pool mesocosms in the presence and absence of mussels. Mesocosms were subjected to a simulated tidal cycle mimicking emersion and immersion patterns of high‐intertidal pools on the central Oregon coast. In the presence of mussels, ammonium accumulated more quickly in the mesocosms, resulting in increased rates of nitrogen assimilation into algal tissues. These increased nitrogen assimilation rates were primarily associated with higher growth rates. In mesocosms containing mussels, Odonthalia individuals added 41% more biomass than in mesocosms without mussels. This direct positive effect of mussels on macroalgal biomass represents an often overlooked interaction between macroalgae and invertebrates. In nutrient‐limited microhabitats, such as high‐intertidal pools, invertebrate‐excreted ammonium is likely an important local‐scale contributor to macroalgal productivity.     

Adaptive visually‐mediated movements of Littorina irrorata (Mollusca: Gastropoda) when displaced from their natural habitat

Littorina irrorata displaced from their natural location amid plant stems in the upper inter‐tidal zone to areas of intertidal zone devoid of vegetation, oriented onshore under all sky and light conditions tested. The responses of snails tested in experimental arenas in the upper intertidal zone indicated that the natural substrate slope of 3 degrees was ignored in favor of movement toward a black paper rectangle. Subsequent releases on natural substrate supported the conclusion that the onshore‐oriented response resulted from visual perception of a dark area (bushes and trees near the high tide line). Where vegetation was equally tall in all directions, snails oriented toward the closest vegetation regardless of the actual onshore direction.     

Tidal activity rhythms and depth distribution of rocky shore fish in an altered intertidal environment

In this note we report on changes of activity level of littoral fish and their use of different microhabitats in an altered intertidal environment, where intertidal fish are never emersed and turbulence is confined to high tides. Despite these atypical conditions, the structure of the assemblage is basically the same found in a typical rocky-shore situation. Two intertidal fish known to possess internal tidal rhythms, Lipophrys pholis and Coryphoblennius galerita, retain those rhythms in these altered conditions, and the associated social changes in L. pholis are also retained. These observations support the studies of Gibson (1971), who showed that changes in hydrostatic pressure were of prime importance in keeping the tidal rhythm entrained. The subtidal Parablennius pilicornis, on the contrary, is more active during low tide than at high tide. The hypothesis that some subtidal species are excluded from the intertidal by a turbulence-avoiding mechanism is discussed.     

Diel and tidal changes in the distribution and feeding habits of Japanese temperate bass Lateolabrax japonicus juveniles in the surf zone of Ariake Bay

Japanese temperate bass Lateolabrax japonicus juveniles recruit to the surf zone and grow by feeding on commonly occurring coastal copepods. However, little is known about diel and tidal patterns in their migration and feeding habits. We sampled wild juveniles during the neap and spring tides, over periods of 24 h, with small seine nets in the sand flat of the eastern part of Ariake Bay, Kyushu, western Japan. In both the neap and spring tides, abundance of juveniles significantly increased during the daytime, being highest around the time of high tide. The relative gut fullness indices of juveniles drastically increased in the morning (0700–0900) and during the flood tide in the daytime, while major prey copepod (Paracalanus spp.) density in the ambient water was relatively constant. We summarized that L. japonicus juveniles would migrate to the surf zone after sunrise to feed on copepods, and then emigrate from the surf zone after sunset. The migratory behavior of L. japonicus juveniles would be influenced by light (daytime) and feeding activity influenced by both light (morning) and tidal condition (flood tide). The intertidal region of the tidal flat was recognized to be one of the important habitats for L. japonicus during their early life history.     

Epibiosis and parasitism of coquina clam Donax spp.: Location,location, location!

Cryptic species of coquina clams Donax fossor and D. variabilis carry the hydroid epibiont Lovenella gracilis and are infected with metacercariae of the monorchiid parasites Lasiotocus trachinoti and L. choanura. The associations among this host–epibiont–parasite system were investigated. Fifty clams were collected at low tide over 3 days in June 2020 in South Carolina from each of three groups: clams with no hydroid from the upper intertidal zone and clams with and without hydroids from the swash zone. Clams were measured, identified using a newly developed PCR-RFLP, and examined for infection by metacercariae. Parasites were identified based on cercarial morphology and on metacercariae habitat in the clams. D. fossor was most often found in the swash zone and D. variabilis in the upper intertidal zone. The hydroid was most often associated with D. fossor, which was more infected by both digeneans than D. variabilis. Mean abundance of metacercariae of L. choanura was higher than that of L. trachinoti in both clams and increased over time for both parasites, because higher infection was correlated with larger clams. Greater time spent in the water by individuals of D. fossor appears to best explain these results, with the presence of the hydroids also being associated with higher infection by metacercariae in this coquina. Integration of D. variabilis in both digenean life cycles appears to lead to a positive outcome for the parasites as prevalence and abundance of infection were high; however, because D. variabilis is most frequent in the upper intertidal, more emersed, zone, it is likely deleterious to the epibiont to establish on this clam.     

The effects of seaweed harvesting on fishes: a response

References Rangeley (1994) has argued that sampling biases, errors in experimental design and low statistical power make the conclusion by Black & Miller (1991), that there was no large impact of an experimental harvest of the seaweedAscophyllum nodosum on fishes, unmerited and misleading. Our study was conducted mainly at two sites close to Lower Argyle, southern Nova Scotia, Canada where harvesting ofAscophyllum nodosum has been carried out continuously for 30 years along-side intense and productive shellfish and finfish fisheries. In southern Nova Scotia, on-going removal ofAscophyllum nodosum with mechanical harvesters is about 17% (Sharpe & Semple 1991); planned annual removal in New Brunswick where Rangeley has worked will be only about 5% (Anon. 1993). The context of our investigation was a small-scale (400 m²) but extreme, experimental removal (100%) of the seaweed. Our focus was on fishes that moved into the intertidal zone as the tide rose in the evening and early morning and were caught in trammel nets, and on the fishes that were retained in a fixed seine that was set at high tide in early morning and the fishes removed at the next low tide. Thus, subject to the constraint on the size of the fishes imposed by the nature of our fishing gear with its stretch mesh of 25 mm, we were concerned with the identity and abundance of fishes that moved in and out of the intertidal zone and their behavioural response to the 400 m² patches of habitat that formed our experimental units. The most striking result was the unexpected, low abundance of fishes caught in our gear.     

Juvenile Chinese mitten crabs (<Emphasis Type="Italic">Eriocheir sinensis</Emphasis>) in the Thames estuary: distribution,movement and possible interactions with the native crab <Emphasis Type="Italic">Carcinus maenas</Emphasis>

The Chinese mitten crab, Eriocheir sinensis is a successful invader. Whilst non-breeding adult E. sinensis have been associated with the destruction of riverbanks, little is known about the ecology of this species in its invaded areas. This is especially true of the juveniles which are a key migratory stage. Intertidal surveys along the Thames estuary indicated an increase in the population since the 1990s. Juvenile E. sinensis were abundant in the sampled upper tidal region of the Thames, refuging under boulders in the intertidal at low tide. Seasonal differences in sampled populations were observed, with a significantly lower abundance of crabs found during winter compared to summer. Mark-recaptures indicated movement in the intertidal occurring during high tide, with an influx of new crabs evident after a single tidal cycle. Endogenous rhythms were also apparent, with peaks in activity occurring corresponding with night-time high tide conditions. E. sinensis juveniles can successfully exclude similar sized native Carcinus maenas from shelters in the laboratory, regardless of which species originally inhabited the shelter. This may have implications for native estuarine Carcinus populations, which can rely on such intertidal shelters for refuges.     

Intercolony variations in movement patterns and foraging behaviors among herring gulls (Larus argentatus) breeding in the eastern Wadden Sea

Herring gulls (Larus argentatus) are opportunistic predators that prefer to forage in the intertidal zone, but an increasing degree of terrestrial foraging has recently been observed. We therefore aimed to analyze the factors influencing foraging behavior and diet composition in the German Wadden Sea. Gulls from three breeding colonies on islands at different distances from the mainland were equipped with GPS data loggers during the incubation seasons in 2012–2015. Logger data were analyzed for 37 individuals, including 1,115 foraging trips. Herring gulls breeding on the island furthest from the mainland had shorter trips (mean total distance = 12.3 km; mean maximum distance = 4.2 km) and preferred to feed on the tidal flats close to the colony, mainly feeding on common cockles (Cerastoderma edule) and shore crabs (Carcinus maenas). In contrast, herring gulls breeding close to the mainland carried out trips with a mean total distance of 26.7 km (mean maximum distance = 9.2 km). These gulls fed on the neobiotic razor clams (Ensis leei) in the intertidal zone, and a larger proportion of time was spent in distant terrestrial habitats on the mainland, feeding on earthworms. δ¹³C and δ¹⁵N values were higher at the colony furthest from the mainland and confirmed a geographical gradient in foraging strategy. Analyses of logger data, pellets, and stable isotopes revealed that herring gulls preferred to forage in intertidal habitats close to the breeding colony, but shifted to terrestrial habitats on the mainland as the tide rose and during the daytime. Reduced prey availability in the vicinity of the breeding colony might force herring gulls to switch to feed on razor clams in the intertidal zone or to use distant terrestrial habitats. Herring gulls may thus act as an indicator for the state of the intertidal system close to their breeding colony.     

SURVIVAL OF FUCOID EMBRYOS IN THE INTERTIDAL ZONE DEPENDS UPON DEVELOPMENTAL STAGE AND MICROHABITAT1

Embryos of the fucoid alga Pelvetia fastigiata (J. Ag.) DeToni were outplanted into the intertidal zone to assess survival during the physical stress brought about by emersion during a single low tide. Survival varied among microhabitats. Under the adult Pelvetia canopy, survival of 6-h-, 24-h-, 48-h-, and 1-wk-old embryos was nearly 100%. Almost all embryos of all ages died in exposed habitats on bare rock or within habitats where the Pelvetia canopy was removed experimentally. However, within red algal turfs, where most juvenile Pelvetia occur, survival was unusually age specific: 24- to 48-h-old embryos survived poorly compared to younger (6 h old) or older embryos (1 wk old). Survival patterns reflected microhabitat temperatures during the experiments. The fate of young post-settlement stages must be studied at these fine temporal and spatial scales to understand the organization of intertidal communities.     

A geomorphological model of intertidal cove marshes with application to wetlands management

Detailed topographic and hydrologic surveys were conducted in five intertidal cove marshes in an outer coastal plain landscape to test the hypothesis that the equilibrium geologic state of intertidal habitats residing in similar landscape situations conforms to a consistent geometric form. The equation V=1571.84A^1.70 (R²=96.2%) describes the relationship between hectares of marsh (A) and cubic meter volume at mean high tide (V). An empirical relationship between tide height and volume was found to obey the power series V_p=L^2.38 (R²=99.6%), where V_p is volume as a percent of full pool and L is water height as a percent of mean high tide. A dimensionless index describing the relationship between area and volume is consistent for each marsh and approaches 0.10. A channel form parameter describing width to channel depth ratios is of consistent value for four of the five marshes. These provide evidence of deterministic rather than stochastic geologic development. The benefits of applying natural basin shape patterns in the design and engineering of created/restored intertidal marshes are highlighted and a generic basin is modeled (based on the geometrical section of a paraboloid retained by simple integration) as an example of the potential applicability of the study.     

The microbiota of intertidal macroalgae Fucus distichus is site-specific and resistant to change following transplant

It is unclear how host-associated microbial communities will be affected by future environmental change. Characterizing how microbiota differ across sites with varying environmental conditions and assessing the stability of the microbiota in response to abiotic variation are critical steps towards predicting outcomes of environmental change. Intertidal organisms are valuable study systems because they experience extreme variation in environmental conditions on tractable timescales such as tide cycles and across small spatial gradients in the intertidal zone. Here we show a widespread intertidal macroalgae, Fucus distichus, hosts site-specific microbiota over small (meters to kilometres) spatial scales. We demonstrate stability of site-specific microbial associations by manipulating the host environment and microbial species pool with common garden and reciprocal transplant experiments. We hypothesized that F. distichus microbiota would readily shift to reflect the contemporary environment due to selective filtering by abiotic conditions and/or colonization by microbes from the new environment or nearby hosts. Instead, F. distichus microbiota was stable for days after transplantation in both the laboratory and field. Our findings expand the current understanding of microbiota dynamics on an intertidal foundation species. These results may also point to adaptations for withstanding short-term environmental variation, in hosts and/or microbes, facilitating stable host–microbial associations.     

PARTITIONING OF FEEDING HABITATS BY WHITEFRONTED PLOVERS CHARADRIUS MARGINATVS AT A DUNE/BEACH INTERFACE

Summary

Van Der Merwe, D., McLachlan A. &; De Ruyck A. M. C. 1992. Partitioning of feeding habitats by Whitefronted Plovers Charadrius marginatus at a dune/beach interface. Ostrich 63:49-57.

The Whitefronted Plover Charadrius marginatus, a resident of the Alexandria dunefield, moves between the beach and dunes to feed. It nests in slacks, one of the many habitats in the dunefield. The main prey items are insects in the dunes and bivalve siphons on the beach. Feeding activity on the beach is determined by the time of day, tide and wind. At wind speeds greater than 10,^s-1 no feeding takes place in the intertidal zone. Below 10m.s^?1 wind speed, feeding is influenced primarily by the time of day and secondarily by the state of the tide. Although feeding takes place at night, this occurs mainly during good light conditions. Feeding activity intensifies at dawn, irrespective of the state of the tide, 61% of total feeding effort occurring on the beach and 39% in the dunes.     

Spatial patterns of the surf zone hyperbenthic fauna of Valdivia Bay (Ecuador)

The present research is a first attempt to study the hyperbenthic fauna of the surf zone of Valdivia Bay (South East Pacific--Ecuador), an exposed low tide terrace--rip beach. The aims of the study were to contribute to the inventory of the surf zone fauna of the tropical southeast Pacific coast, to investigate spatial distribution patterns along the bay and to search for possible tidal effects on the hyperbenthic composition. Samples were taken during daylight with a hyperbenthic sledge on 6 consecutive days in August 1999 at high tide, low tide and mid tide. The hyperbenthic community was characterized by quantifying the higher taxa, their density and the relative composition of the dominant groups. No tidal effect could be observed, but two main geographically distinct hyperbenthic assemblages were distinguished along the bay, related to hydrodynamic factors (local current velocity, intertidal beach slope and suspended particulate matter). In the turbulent northern part of the bay the highest densities were encountered and hyperbenthos was, next to the dominant mysid Metamysidopsissp., mainly composed of planktonic organisms (calanoid copepods, chaetognaths and fish eggs). In the calmer southern part of the bay Metamysidopsissp. dominated as well, but the community was completed with other mysid species, and early life stages of Brachyura and fish. Most striking was the general dominance of the mysid Metamysidopsis sp. in all the samples (97%, max. density of 62000 ind. 100 m^-2) and the high amount of unknown species. Penaeid shrimp larvae, important for the local shrimp industry, were only found in very low densities during the sampling period (1%). Compared to other studies on the whole surf zone hyperbenthic community of sandy beaches, the average densities encountered in Valdivia Bay can be considered to be relatively high (2500--6000 ind. 100 m^-2). Although limited in time and performed with a limited taxonomic resolution, the results indicate a high contribution of early life stages of invertebrate and fish species to the biodiversity of the intertidal hyperbenthic community in comparison with temperate regions.