Macrobenthic communities in Hong Kong waters: Comparison between 2001 and 2012 and potential link to pollution control

Podarkeopsischinensis sp. nov. (Annelida, Hesionidae) from southeastern China

Podarkeopsischinensissp. nov. (Annelida, Hesionidae) is described based on specimens collected from the coast of southeast China. It is the first Podarkeopsis species described from the Indo-Pacific, although there are already nine valid Podarkeopsis species known from other parts of the world. This new species can be distinguished from the other Podarkeopsis species in having a palpostyle as long as the palpophore and double aciculae in both notopodia and neuropodia, and in bearing bifid furcate chaetae which have a smooth base on the shorter tine. A phylogenetic analysis based on the concatenated sequences of five gene fragments (COI, 16S rRNA, 18S rRNA, 28S rRNA, and histone H3) from 18 specimens of P.chinensissp. nov. showed that they formed a monophyletic clade that is sister to P.levifuscina. K2P genetic distances indicated that the four gene fragments (COI, 16S rRNA, 18S rRNA, and 28S rRNA) of P.chinensissp. nov. diverged from the corresponding sequences of the closest related species of Podarkeopsis in GenBank and BOLD Systems by 21.1-27.5%, 20.3-23.1%, 0.1-0.2%, and 2.1-3.2%. An identification key is provided for species in the genus Podarkeopsis.

Temporal and Spatial Trends in Benthic Infauna and Potential Drivers, in a Highly Tidal Estuary in Atlantic Canada

Infaunal invertebrate communities of coastal marine sediments are often impacted by human activities, particularly in harbours and estuaries. However, while many studies have attempted to identify the key factors affecting benthic infauna, few have done so for highly energetic tidal estuaries. Samples were collected over a decade (2011-2020) from a series of reference sites in Saint John Harbour (45.25° N, 66.05° W), a highly tidal estuary in the Bay of Fundy, Canada. These data were used to examine spatial and temporal trends in infaunal invertebrate communities and sediment properties and to determine the extent to which the biological patterns were driven by measured physical and chemical variables. There were substantial differences among sites in infaunal invertebrate abundance (median ranging from 688 to 13,700 individuals per square meter), infaunal species richness (median ranging from 8 to 22), and Shannon diversity (median ranging from 1.26 to 2.34); multivariate analysis also revealed variation in species composition among sites. Sediment contaminant concentrations also varied among sites, but differences tended to be smaller (e.g. median chromium concentrations ranging from 21.6 to 27.6 mg/kg). Sample contaminant concentrations were all below probable effect levels, and almost all below threshold effect levels (Canadian interim sediment quality guidelines), but relationships with biological data were still detectable. However, physical variables (depth, sediment characteristics) were better predictors of biological variables and community composition. These results confirm the importance of physical factors in shaping infaunal communities in soft-sediment habitats in tidally influenced coastal waters.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12237-023-01222-w.

Responses of the benthic environment to reduction in anthropogenic nutrient loading in the Seto Inland Sea (Japan), based on M-AMBI assessment

Deterioration of the sediment environment and benthic ecosystem is an undesirable effect of eutrophication, but little is known about the response of macrobenthic communities to eutrophication and their long-term recovery. In the present study, temporal changes in benthic ecological status, associated with reductions in anthropogenic impacts on a largest semi-enclosed sea in Japan, were determined using long-term monitoring data from water and sediment quality based on the multivariate AZTI Marine Biotic Index (M-AMBI), focusing on spatial differences in anthropogenic impacts. Several sub-areas were classified based on Chlorophyll a (Chl.a) concentrations in surface water during the 1980s. Chl.a concentrations decreased in all sub-areas except the sub-area with <2 μg Chl.a L^-1 from the 1990s-2010s. On the other hand, total organic carbon contents in sediment decreased and M-AMBI values increased in all sub-areas during this period may be due to reduced lateral organic matter advection from surrounding areas.

Recovery of tropical marine benthos after a trawl ban demonstrates linkage between abiotic and biotic changes

Bottom trawling, which is highly detrimental to seabed habitats, has been banned in some jurisdictions to mitigate the problems of habitat destruction and overfishing. However, most reports of ecosystem responses to trawling impacts originate from temperate latitudes, focusing on commercial species, and recovery of invertebrate macrobenthos from trawl ban has hardly ever been studied in the tropics. In Hong Kong (lat. 22.4°N), a history of intensive trawling with various types of gears has long degraded coastal ecosystems. To facilitate the recovery of fisheries resources and associated benthic ecosystems, the Government of the Hong Kong Special Administrative Region implemented a territory-wide trawl ban on December 31, 2012. Comparison of surveys conducted in June 2012 (before the trawl ban) and June 2015 (2.5 years after the ban) revealed higher organic contents in sediment and lower suspended-solid loads in water column, as well as a significant increase in site-based abundance, species richness, functional diversity and among-site similarity of macrobenthos after the trawl ban. Our results suggest that the imposition of a trawl ban can be an effective measure for biodiversity conservation in tropical coastal waters.

How do spatial and environmental factors shape the structure of a coastal macrobenthic community and meroplanktonic larvae cohort? Evidence from Daya Bay

We examined the relative importance of spatial processes (dispersal-related) and environmental processes (environmental selection-related) in community structure for macrobenthos (including juveniles and adults) and meroplanktonic larvae in the subtidal areas of Daya Bay, China. We found that both macrobenthos and meroplanktonic larvae showed similar spatial patterns, both following the distance-decay relationship. The results of variation partitioning analysis (VPA) showed the roles of both spatial and environmental factors in governing the assembly of both communities, although both explained only a small (slightly larger for spatial factor) fraction of the community variation. We also found that macrobenthos were more affected by spatial processes than meroplanktonic larvae. In addition, we highlight that the mechanisms determining community structure change according to the spatial extent considered.

Redescription of Leocrates chinensis Kinberg, 1866 (Annelida, Hesionidae)

Zhi Wang, Jian-Wen Qiu, and Sergio I. Salazar-Vallejo (2018) Leocrates chinensis Kinberg, 1866 is the type species of Leocrates Kinberg, 1866 (Annelida, Hesionidae). Its original description, based upon a single specimen collected in Hong Kong waters, was brief; its illustrations were published almost 50 years afterwards, and the type specimen was dried out before it could be redescribed. The late Marian Pettibone redescribed the species in 1970 but her illustrations of the species were based on specimens from the Mediterranean Sea, the Virgin Islands, and Samoa, not Hong Kong. In order to define the morphological features, we herein redescribe this species based upon newly collected specimens from the type locality. This species is characterized by the following features: prostomium subrectangular with a posterior notch, lateral antennae slightly longer than palps, palps with palpophores about 2.5 times longer than palpostyles, anterior eyes twice larger than posterior ones, slightly emarginated, posterior ones circular, median antenna fixed slightly ahead of posterior eyes, nuchal organs C-shaped; pharynx with a prominent dorsal papilla, a mid-dorsal jaw and a mid-ventral jaw; first four chaetigers subbiramous, others biramous with neuroacicular lobes blunt, as long as wide, or longer than wide; notochaetae spinulose capillaries; most neurochaetae with blades bidentate, guards approaching subdistal tooth; a few neurochaetae with long, tapered hoods. A key to identify all species in the genus is also included.

Trophic and growth baseline of dominant subtidal gastropods in contrasting subtropical marine environments

Using ¹³C/¹²C, ¹⁵N/¹⁴N and ¹⁸O/¹⁶O isotopes, the trophic relationship and growth estimation were analyzed in gastropods Nassarius siquijorensis, Murex trapa and Turritella bacillum and their potential food sources and predators in summer and winter from estuarine and oceanic environments in subtropical Hong Kong. Results of δ¹³C and δ¹⁵N values and isotopic mixing model revealed N. siquijorensis and M. trapa were one trophic level higher than T. bacillum, in which its main food source was particulate organic matter (POM) whereas N. siquijorensis largely consumed POM and polychaetes and M. trapa also preyed on other gastropods. Crabs were the major predator of gastropods. Organisms collected from oceanic waters were more ¹³C enriched than from estuarine waters, reflecting different carbon food sources from marine or terrestrial origin. The δ¹⁸O profile from shell carbonate suggested these gastropods were one to two years old. T. bacillum exhibited faster summer growth than the other two species.

Different effects of reclamation methods on macrobenthos community structure in the Yangtze Estuary, China

The effects of enclosed, semi-closed, and opened reclamation methods on the macrobenthos community structure were investigated. Compared with their paired controls, water salinity decreased sharply in the enclosed reclamation region with no apparent change in the opened reclamation region. Declining species and biodiversity was observed in the reclamation regions, but the extent of this declining trend was weaker in the semi-closed and opened reclamations than in the enclosed reclamation region. The ABC curve indicated that the enclosed reclamation was disturbed, whereas the semi-closed and opened reclamations were undisturbed. Taken together, these results suggest that reclamation may have a negative effect on the community and health status of macrobenthos in the intertidal wetlands of the Yangtze Estuary. Semi-closed and opened reclamation methods may mitigate the problem of a salinity decrease caused by enclosed reclamation, while also having a relatively weaker negative effect on community structure and wetland habitat.