Marine Biodiversity Special Feature
The abundance and seasonal change of large-sized tintinnids were studied in Laizhou Bay. Large-sized tintinnids were collected by vertical towing using a shallow sea type III plankton net (open area 0.1 m2, mesh size 76 μm) during 9 cruises between May and November of 2011 and from March to April, 2012. The samples were fixed in formalin solution to a final concentration of 5% and counted using an inverted microscope in the laboratory. We sampled 8 stations to avoid fluctuations over a short time period. The purpose of this study was to characterize seasonal change of the large-sized tintinnid community. Maximum tintinnid species richness was 19 in August and minimum was 5 in May. Tintinnid abundance ranged from 0 ind./L to 318 ind./L. Average abundance at all stations was highest (63 ind./L) in July and lowest (2 ind./L) in March, and there was a secondary peak of 48 ind./L in May. The abundance of Codonellopsis mobilis and Tintinnopsis chinglanensis were more than 50 ind./L. Agglutinated species occurred from March to November, while the hyaline species only occurred from June to September when the temperature was > 15°C. Codonellopsis mobilis occurred from March to November. The number of dominant species ranged from 1 in May, to 8 in August. Codonellopsis mobilis was a dominant species during all time periods and this one species significantly influenced the pattern of total ciliate abundance. Using the average abundance data of 8 stations, two distinct cluster groups were observed (30% similarity): cluster I (July to September) and cluster II (March to June, October to November). The cluster results showed that there was a seasonal change of the large-sized tintinnid community. Average abundance and species richness were not significantly correlated with temperature and salinity.
With an aim of describing the influence of coralline algae on other macroalgae and benthic invertebrates in the intertidal zone of the Nanji Islands, an investigation of such organism assemblages was conducted in the Nanji Archipelago Marine Nature Reserve between May 2012 and February 2013. Shannon-Wiener index and Pielou's evenness indices were calculated for macroalgae (including coralline algae), non-Corallinaceae macroalgae (excluding coralline algae) and benthic invertebrates. In addition, the functional diversity of the benthic community was estimated using Rao's Q. Our results are as follows: (1) A total of 52 species of macroalgae belonging to 3 phyla, 3 classes, 16 orders, 21 families and 41 genera were found; 5 species among them belonged to coralline algae; (2) The dominance of coralline algae has reached a high level in the intertidal zone of the Nanji Islands except in the high tidal zone where relatively few macroalgae exist. The biomass of coralline alga accounted for 68.9% of the total algae biomass. Shannon-Wiener indices of macroalgae diversity varied from 1.638-4.044, and non-Corallinaceae macroalgae varied from 1.495- 3.809, while benthic invertebrates’ varied from 5.2890-6.917. Pielou’s evenness of macroalgae communities varied from 0.819-0.971, and non-Corallinaceae macroalgae varied from 0.930-0.973; benthic invertebrates ranged from 0.967 to 0.988; (3) Regression analyses between dominance of coralline algae and Shannon-Wiener and Pielou's evenness indices of macroalgae communities suggested that coralline algae may be reducing the species diversity of macroalgae. The result of correlation analysis between dominance of coralline algae and Shannon-Wiener index, Pielou's evenness of benthic invertebrates showed no significant correlation. (4) The dominance of coralline algae and Rao's Q of benthic invertebrates in low tidal zone were both higher than those in middle tidal zone, but the correlation analysis showed no significant correlation between them. Based on our results, we concluded that: well-adapted coralline algae species may have reduced the species diversity of other macroalgae in these systems via interspecific competition; meanwhile, the benthic invertebrates, perhaps because of their higher dispersal abilities and more diverse life histories relative to macroalgae, were not affected in terms of species or functional diversity by coralline algae.
The aims of our study were to (1) uncover new reef fish species records using the underwater visual census method; and (2) analyze the fish community structure according to trophic groups and its response to water quality changes. The fishes on six reefs (Yongxing Island, Dongdao Island, Lingyang Atoll, Jinyin Island, Huaguang Atoll, and Zhongjian Island) along the Xisha Archipelago were investigated in May-June, 2006 using underwater visual censuses. The fishes we recorded belong to 29 families, 71 genera and 119 species. The number of newly recorded species was 50. The number of fish species increased to 717 in the Xisha area since the 1950’s. The species number and Shannon-Wiener diversity were both highest on the western reef of Yongxing Island. Most fish species were distributed narrowly in small areas. The dominant assemblages were the planktivores and bottom invertebrate feeders. The rare assemblages were the herbivores, the omnivores, and the top predator, the piscivores. The structure of trophic groups indicated that most coral reef systems were relatively healthy. The percentage of total abundance (and biomass) comprised by omnivores was largest on the western reef of Yongxing Island compared to other reefs, suggesting that the fish community structure had responded to water eutrophication around Yongxing Island.
In order to assess the ecological impacts of Spartina alterniflora on mangrove ecosystems, we investigated macro-invertebrate communities in S. alterniflora wetlands and a mangrove wetland between October 2012 and September 2013, in the Xicungang estuary, Guangxi Zhuang Autonomous Region. The species composition, biomass and diversity of macro-invertebrates were compared at different times between the mangrove habitat and S. alterniflora community. Sixteen species from Arthropoda, Mollusca, Annelida, Cnidadia and Sipuncula were collected from the two habitats. Twelve species were found in mangrove wetlands whereas 10 species were found in S. alterniflora wetlands. Perhaps due to the invasion of S. alterniflora, Glauconome chinensis became the predominant species, leading to a greater macro-invertebrate biomass in S. alterniflora wetlands than in mangrove wetland. On the other hand, the Margalef, Shannon-Wiener index, Simpson and Pieous diversity indices of macro-invertebrates were lower in S. alterniflora habitat than in mangrove habitat. Two-way ANOVA was used to analyze the effect of sampling periods and habitats on the number of species, biomass and diversity indices of macro-invertebrates. Our results showed that Shannon- Wiener index and Simpson diversity indices differed between the two habitats, the Margalef and Pieous diversity indices differed among sampling periods, number of species and biomass were affected by both habitats and sampling periods. Based on multiple linear regression analyses, macro-invertebrate biomass was related to the density of S. alterniflora, and Shannon-Wiener, Simpson diversity and species richness of macro-invertebrates were all related with the height of S. alterniflora. According to our NMDS (non-metric multidimensional scaling) analysis, macro-invertebrate communities in S. alterniflora habitat mainly differed from those of mangrove habitats due to sampling periods. In conclusion, the invasion of S. alterniflora in mangrove wetlands in Xicungang estuary increased the biomass of macro-invertebrates, while decreased the diversity of them, and also changed the community structure of macro-invertebrate assemblages.
Taxonomic studies on the family Pyrocystaceae are scarce because of the group’s special life cycle and complicated taxonomic history. In this study, a detailed literature review of Pyrocystaceae is presented, and cysts of 11 species belonging to Pyrocystaceae are studied using morphological taxonomy methods. We believe that one species should be moved to genus Dissodinium, the remaining 10 species (including 2 varieties and 2 formas) are more reasonably kept in genus Pyrocystis. We also present a morphological description of each species. Furthermore, we believe that the taxonomic relationships between Dissodinium pseudolunula and Pyrocystis lunula, P. elegans and P. robusta require further study.
We analyzed the structure, distribution, and seasonal changes of planktonic copepod communities, as well as their relationships with environmental factors using data collected from 21 stations in the northwest coastal waters off Hainan Island between November 2008 and July 2009. A total of 44 species of planktonic copepods was identified, with 25, 23, 22, and 23 species found in autumn (November), winter (January), spring (April) and summer (July), respectively. The dominant species were mainly warm water species, such as Canthocalanus pauper, Subeucalanus subcrassus, Temora turbinate, Acartia spinicauda, Calanopia elliptica and Euchaeta concinna, etc. There were significant changes in copepod abundance among seasons; total copepod abundance was highest in winter with 409 ind./m3, followed by autumn with 144 ind./m3, spring with 55 ind./m3 and summer with 17 ind./m3, respectively. Distributional data showed that an area of high copepod density appeared in the southern portion of the study area in winter, while there was an area of high copepod density in the center of the survey area in autumn. Copepod abundance was higher in deeper waters, and lower in the coastal areas in spring and summer. Species diversity index was highest in summer and followed by spring, autumn and winter in turn. The evenness index of spring and summer copepod communities was higher than those of autumn and winter. The structure of these planktonic copepod communities reflects tropical and subtropical floristic characteristics. Species composition varied significantly with season, and copepod abundance was noticeably affected by water temperature and diatom cell abundance. We detected no obvious correlationship between copepod abundance and salinity.
To study the relationship between macrobenthic fauna and environmental factors, we investigated four transects from coast to deep-sea waters near the Pearl Estuary in the northern South China Sea from July -August 2006 (Summer, wet season), April-May 2007 (Spring, normal water season), and October-December 2007 (Autumn, dry season). A total of 273 species, 256 species and 148 species were identified in spring, summer and autumn, respectively. Macrobenthic fauna belonging to the Annelida phylum had the greatest species richest, followed by Arthropoda, Mollusca, and Echinodermata. The species richness, abundance and biomass of macrobenthic fauna increased from estuary sites to coastal sites, and decreased from coastal sites to deep-sea sites. The Shannon-Wiener index of macrobenthic fauna was higher in coastal sites than those in estuary and deep-sea sites. The species evenness of macrobenthic fauna was the highest in deep-sea sites, followed by coast and estuary sites. The k-dominance curves of macrobenthic fauna were higher in estuary and deep-sea sites than that in coastal sites. These results show that the macrobenthic biodiversity was the highest in coastal sites. Species richness, abundance, and biomass of macrobenthic fauna are negatively correlated with water depth in spring and autumn, but only biomass of macrobenthic fauna is negatively correlated with water depth in summer. The species richness, abundance, Shannon-Wiener index, and species evenness of macrobenthic fauna are positively correlated with salinity in the bottom of the water column in summer, but are not correlated in spring and autumn.
In order to study the spatial and temporal variations of invertebrate community structure and diversity in the Yangtze River Estuary and its adjacent waters, we investigated invertebrate populations using fixed double bottom trawling during the springs of 1999-2012. Results show that: (1) there were 41 invertebrate species recorded, belonging to 6 classes, 10 orders, and 23 families. Crustaceans were the most recorded species (26 species), followed by mollusks (13 species). The number of recorded species decreased over the sampling period; (2) dominant invertebrates included Loligo japonica, Portunus trituberculatus, Palaemon gravieri, and Trachypenaeus curvirostris. There was significant inter-annual variation but Loligo japonica was the most dominant species across the sampling period; (3) there was significant inter-annual variation in invertebrate abundance, species richness and diversity in the estuary. Abundance, species richness and diversity peaked in 1999 and 2001, and increased after 2004; (4) there were 2 or 3 species assemblages in the estuary, which had different indicator species; (5) the temporal variation in the invertebrate community can be divided into three distinct periods. 1999-2001 featured high species diversity, 2004-2007 saw a decrease to the lowest species diversity, and by 2009-2012 diversity had recovered but was still below the level of 1999-2001. A decline in crab populations has resulted in the decline of overall invertebrate biomass, while deficiencies at high trophic levels has promoted a diversification of invertebrate diet.
The diversity and trophic levels of fish species in Tong’an Bay were described based on monthly set net fishing surveys from April 2012 to March 2013. A total of 112 species belonging to 88 genera, 53 families and 15 orders were recorded. According to their habitat strata, the fishes were grouped into 3 types, among them 15 species were pelagic, 18 near demersal, and 79 demersal. According to adaptation to temperature, the fishes were divided into 2 types, 84 species were warm water and the other 28 were warm-temperate species. In terms of food habits, there were 4 types, of which 8 species were omnivores, 71 lower carnivorous, 30 middle carnivorous and 3 higher carnivorous. Tachysurus sinensis was the dominant species in summer, autumn and winter, while Polydactylus sextarius, Butis koilomatodon and Tridentiger barbatus were the dominant species in spring and winter. The highest body mass and individual Shannon-Wiener diversity index were 3.26 and 3.29 in November, and the lowest values were 1.78 and 1.77 in February, respectively. The fish community showed distinct seasonal changes, with the lowest monthly change rate of fishes of 40.1% in June, and the highest was 68.6% in March. The mean trophic level also showed significant changes, the minimum was 3.02 in March, the maximum was 3.92 in January, and the average mean trophic level was 3.52. Comparing our data set with previous data from 2003-2004, we found that the species number, species composition and the dominant species in Tong’an Bay all changed significantly. Overfishing, habitat loss and environmental pollution were identified as main factors causing the decline in fish diversity in Tong’an Bay.
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