Jassa (Crustacea: Amphipoda): a new morphological and molecular assessment of the genus

The amphipod genus Jassa Leach, 1814 now comprises 24 species that occur in temperate regions of both hemispheres on solid substrates from the lower intertidal zone to 500 m depth. The propensity for some species to form dense colonies in water intake structures and offshore platforms has brought them to attention as an unwanted pest. Based on the examination of ~25,000 specimens from ~1,100 museum and private collections, it is evident that some species of Jassa have been transported by human vectors since at least the 19th century and now occur widely. Their colonial, tube-living habit enables such transport, and collection records document them on ships, buoys and portable water systems as well as on natural movable substrates such as logs, drift algae and larger crustaceans. Because Jassa can be so readily found, but species discrimination has had a problematic history, the purpose of this monograph is to assist researchers to identify species through illustrations, descriptions, keys and habitat summaries. Seven species which were named in the 19th century but whose names have lapsed are placed in the context of currently known species. Two new species, J. laurieae n. sp. and J. kimi n. sp. are described, and J. monodon (Heller, 1866) and J. valida (Dana, 1853) are resurrected. Jassa mendozai Winfield et al., 2021 is submerged under J. valida, and J. cadetta Krapp et al., 2008 and J. trinacriae Krapp et al., 2010 are submerged under J. slatteryi Conlan, 1990. Morphological differences are related to current understanding of growth, behaviour and ecology. CO1 analysis suggests a Southern Hemisphere origin with diversification northward and an evolutionary direction toward greater physiological plasticity, leading to success in long distance transport and establishment in exotic locations. Correct identification of Jassa world-wide will facilitate further research on this ecologically important genus and will allow for differentiation of indigenous from exotic introductions.

Characterization of Intertidal Bar Morphodynamics Using a Bi-Annual LiDAR Dataset

Intertidal bars are common features on meso-and macro-tidal sandy beaches with low to moderate wave energy environments. Understanding their morphodynamics is, hence, crucial for enhancing our knowledge on beach processes which is beneficial for coastal management. However, most studies have been limited by assessing bar systems two-dimensionally and typically over the short-term. Morphology and dynamics of an intertidal bar system in a macro-tidal environment have been investigated using bi-annual LiDAR topographic surveys over a period of seven years and along 3.2 km at Groenendijk beach (Belgium). The detected bars demonstrate that a morphology of an intertidal bar is permanently on the beach. However, these individual features are dynamic and highly mobile over the course of half a year. The mean height and width of the bars were 1.1 and 82 m, respectively. The highest, steepest, and asymmetric features were found on the upper beach, while they were least developed in the lower intertidal zone. The bars were evenly distributed over the entire intertidal beach, but the largest concentration observed around the mean sea level indicated the occurrence at preferential locations. The most significant net change across the beach occurs between the mean sea level and mean-high-water neap which corroborates with the profile mobility pattern. The seasonal variability of the bar morphology is moderately related to the seasonally driven changes in storm and wave regime forcings. However, a distinct relationship may be inhibited by the complex combination of forcing-, relaxation time- and feedback-dominated response. This work conducted from bi-annual LiDAR surveys has provided an unprecedented insight into the complex spatial organization of intertidal bars as well as their variability in time from seasonal to annual scale.

Controls of channel morphodynamics on the intertidal dune morphodynamics and associated bedload transport in the open-coast macrotidal flats

<p>Intertidal dune morphodynamics is closely tied to bedload transport that is variable in time and space due to the interplay between tide, wave and runoff discharge. Surprisingly the control of intertidal channel morphology on the dune morphodynamics and related bedload transport is scarcely documented. Actively migrating dunes are widely developed in the lower intertidal zone of Yeochari tidal flat in the northern Gyeonggi Bay, west coast of Korea. High-resolution aerial images, high-precision transect profiles, and hydrodynamic dataset were repeatedly obtained and analyzed to quantify the intertidal dune morphodynamics and associated bedload transport, and to address the role of channel morphodynamics. During the research period, the intertidal channel became more sinuous and an ebb barb arose concurrently at the upstream of the channel point bar. The ebb barb exerted a key role in the downstream delivery of fine-grained sediments onto the areas covered by dunes and the intertidal channel by reinforcing ebb currents with a pronounced time-velocity asymmetry. The presence of the ebb barb resulted in a rapid decrease of the width/depth ratio of the channel that had migrated laterally 130 m in six years. After the ebb-barb development, the heights and steepness (height/wavelength) of dunes on the point bar and near the ebb barb decreased notably. Simultaneously dune migration rate had increased from 0.5 m/day to 2.5 m/day, which decreases away from the channel. Bedload transport estimated by using Meyer-Peter and Muller (MPM) equation and Dune-Tracking Method (DTM) also decreases away from the channel. Bedload transport calculated by DTM (qb<sub>DTM</sub>, 0.03-0.38 m<sup>2</sup>/day) is much smaller than that estimated by MPM (qb<sub>MPM</sub>, 0.10-4.17 m<sup>2</sup>/day) by a factor of 1.5 to 62. The discrepancy ratio between the two bedload estimates (qb<sub>MPM</sub>/qb<sub>DTM</sub>) increases toward the channel and the ebb barb. Downslope flow toward the channel during the late stage of ebb tide may account for the underestimation of qb<sub>DTM</sub> by facilitating downslope sediment transport that reduced the dune steepness with the infilling of dune trough. The present study showcased a dynamic response of the dune morphodynamics and associated bedload transport in the open-coast tidal flats to the changes in the channel morphodynamics that is controlled by seasonal runoff discharge as well as tidal currents.</p>

First record of the red alga Tiffaniella gorgonea: an introduced species in the Mediterranean Sea

The red algaTiffaniella gorgonea(Wrangeliaceae, Rhodophyta) is found and described for the first time from the Mediterranean Sea. This species was collected growing as epiphyte on three species ofCodiumin the lower intertidal zone from Dalya, Cabo Negro and Al-Hoceima on the Mediterranean coast of Morocco. Moroccan specimens were studied in detail and compared with two other closely related species reported previously from Morocco and the Mediterranean Sea. A key to the Mediterranean and Moroccan species ofTiffaniellais provided. Habitat, geographical distribution, and the possible vector of introduction of the new alien are presented and discussed in this work. Taxonomic remarks, a description and images of the macroscopic and microscopic characters are provided for this taxon.

KEANEKARAGAMAN GASTROPODA PADA ZONA INTERTIDAL TENGAH (MIDLE INTERTIDAL ZONE) DAN ZONA INTERTIDAL BAWAH (LOWER INTERTIDAL ZONE) DAERAH PADANG LAMUN DESA WAAI

Background: Seagrass grows and spreads in nearly all parts of the intertidal zone. Waai village has characteristic sloping coastal water and have different patterns of zonation of seagrass in the intertidal zone's third-impact on the presence of seagrass and the organisms in it. Methods: The study was conducted in coastal waters Waai village, in the middle of the intertidal zone (middle intertidal zone) and the lower intertidal zone (lower zone intertidal). The samples in this study are all kinds of gastropods found in each plot observation station of 100 plots. Gastropod species diversity using diversity index formula Shannon - Wiener referred to under Ludwig and Reynolds. Results: From the results of the study found 8 species of gastropods and has a diversity index that is currently in the middle intertidal zone, the average diversity index of 1.76, while in the lower intertidal zone, the average gastropod diversity index was 1.45. Conclusion: diversity index indicates the middle intertidal zone, the average diversity index of 1.76, while in the lower intertidal zone, the average index of diversity of gastropods is 1.45, this is caused by the different seagrass zonation patterns and habits of the people who frequently uses seagrass area for commercial purposes.

Parasites alter host phenotype and may create a new ecological niche for snail hosts

By modifying the behaviour and morphology of hosts, parasites may strongly impact host individuals, populations and communities. We examined the effects of a common trematode parasite on its snail host, Batillaria cumingi (Batillariidae). This widespread snail is usually the most abundant invertebrate in salt marshes and mudflats of the northeastern coast of Asia. More than half (52.6%, n =1360) of the snails in our study were infected. We found that snails living in the lower intertidal zone were markedly larger and exhibited different shell morphology than those in the upper intertidal zone. The large morphotypes in the lower tidal zone were all infected by the trematode, Cercaria batillariae (Heterophyidae). We used a transplant experiment, a mark-and-recapture experiment and stable carbon isotope ratios to reveal that snails infected by the trematode move to the lower intertidal zone, resume growth after maturation and consume different resources. By simultaneously changing the morphology and behaviour of individual hosts, this parasite alters the demographics and potentially modifies resource use of the snail population. Since trematodes are common and often abundant in marine and freshwater habitats throughout the world, their effects potentially alter food webs in many systems.

The significance of contrasting feeding strategies on the reproductive cycle in two coexisting tellinacean bivalves

Semele solida and Tagelus (Tagelus) dombeii are two tellinacean bivalves which coexist in the lower intertidal zone of a sandflat in south-central Chile but follow different feeding strategies. Wheras T. (T.) dombeii is a suspension-feeder, S. solida is a facultative deposit-feeder. In this study, digestive gland indices and reproductive cycles were described in relation to annual food availability and related to their feeding modes. Results showed that gonadic index cycles were similar for both species, with highest values being observed during the spring when water temperature was still on the rise and microflagellate and centric diatom density was at its peak. However, histological analyses indicated that the spawning period of T. (T.) dombeii extended from November 1995 to March 1996 and from August 1996 to January 1997, whereas S. solida presented a continuous spawning period that extended from September 1995 to December 1996. Results suggest that extended spawning throughout the winter by S. solida is a consequence of its ability to feed on bottom deposits when food in suspension is low.

Numbers of naked amoebae inhabiting the intertidal zone of two geographically separate sandy beaches

Numbers of naked amoebae (Gymnamoebae) inhabiting the lower intertidal zone of two sandy beaches were estimated using a novel enrichment cultivation method. Samples were collected between June and September, 1999. Beach sand at Kames Bay, Isle of Cumbrae, Scotland contained on average 2604 amoebae cm−3 while at Dania Beach, Florida, USA, sand harboured 4236 amoebae cm−3. This is the first study to focus on the abundance of naked amoebae inhabiting a sandy beach. These numbers are higher than densities generally reported for shallow subtidal sands and show that amoebae must be considered in future studies on the dynamics of sandy beach communities.