Bioindicator role of tintinnid (Protozoa: Ciliophora) for water quality monitoring in Kalpakkam, Tamil Nadu, south east coast of India

Protozoan communities serve as a strong indicator of water quality in the Nile River

The relationship between the protozoan communities and environmental variables was studied in the Nile River to evaluate their potential as water quality indicators. Protozoans were sampled monthly at six sampling sites in the Nile's Damietta Branch across a spatial gradient of environmental conditions during a 1-year cycle (February 2016-January 2017). The Protozoa community was comprised of 54 species belonging to six main heterotrophic Protozoa phyla. The abundance (average, 1089 ± 576.18 individuals L-1) and biomass (average, 86.60 ± 106.13 μg L-1) were comparable between sites. Ciliates comprised the majority of protozoan species richness (30 species), abundance (79.72%), and biomass (82.90%). Cluster analysis resulted in the distribution of protozoan species into three groups, with the most dominant species being the omnivorous ciliate Paradileptus elephantinus. Aluminium, fluoride, and turbidity negatively affected abundance and biomass, while dissolved oxygen and potassium positively impacted biomass. Of the dominant species recorded over the study area, the amoebozoa Centropyxis aculeata was associated with runoff variables, while the bacterivorous ciliates Colpidium colpoda, Glaucoma scintillans, and Vorticella convallaria were related to the abundance of heterotrophic bacteria, phytoplankton biomass, and total organic carbon. Total dissolved salts, PO4, NH3, NO2, dissolved oxygen, and total organic carbon were the strongest causative factors for protozoa distribution. The α-Mesosaprobic environment at site VI confirmed a high load of agricultural runoffs compared to other sites. This study demonstrates that protozoans can be a potential bioindicator of water quality status in this subtropical freshwater river system.

Diatom bloom trigger notable variations in microzooplanktonic ciliate composition, body-size spectrum and biotic-abiotic interaction in the Arctic Ocean

How microzooplanktonic ciliate adaptative strategies differ across diatom bloom and non-diatom bloom areas in the Arctic Ocean remains poorly documented. To address this gap, two different situations were categorized in the Arctic Ocean at summer 2023: diatom bloom stations (DBS) (genus Thalassiosira, chain-like) and non-diatom bloom stations (nDBS). Total abundance of ciliate at 3 m and 25 m in DBS was 2.8 and 1.8 folds higher than in nDBS, respectively. Aloricate ciliates were singled out in both DBS and nDBS, whilst their average abundance and biomass of large size-fraction (>50 μm) in former were 4.5-5.6 folds higher than in latter. Regarding tintinnids, high abundance of Ptychocylis acuta (Bering Strait species) mainly occurred at DBS, coupled with distribution of co-occurring Pacific-origin species Salpingella sp.1, collectively suggested a strong intrusion of Pacific Inflow during summer 2023. Additionally, presence of high abundance of Acanthostomella norvegica and genus Parafavella in nDBS might indicate the trajectory of the Transpolar Drift. Alternatively, tintinnids can serve as credible bioindicators for either monitoring currents or evaluating microzooplankton Borealization. Average abundance of total ciliate within 15-135 μm body-size spectrum in DBS was higher than nDBS. Moreover, spearman's rank correlation between biotic and abiotic analysis revealed that temperature and dissolved oxygen at DBS determined tintinnid species richness and ciliate total abundance, respectively. The results clearly demonstrate that remarkable divergences in large size-fraction of ciliate abundance between DBS and nDBS validate their irreplaceable role in controlling phytoplankton outbreak and associated biological processes in polar seas.

Latitudinal pronounced variations in tintinnid (Ciliophora) community at surface waters from the South China Sea to the Yellow Sea: Oceanic-to-neritic species shift, biotic-abiotic interaction and future prediction

The oceanic-to-neritic species shift of microzooplanktonic tintinnids and their interaction with relevant abiotic variables are two crucial processes in the marine ecosystem. However, these processes remain poorly documented in China's marginal seas. In the summer of 2022, we investigated the community structure of pelagic tintinnids in surface waters from the South China Sea (SCS) to the Yellow Sea (YS), passing through the East China Sea (ECS). A number of 58 species from 23 genera were identified, with 36 and 22 species belonging to oceanic and neritic genera, respectively. The abundance proportion of oceanic and neritic genera exhibited a decreasing and increasing trend, respectively, from the SCS to YS. Furthermore, four distinctive tintinnid community groups were classified based on cluster analysis using tintinnid species and abundance data, and the position of southern Taiwan Strait was identified as the "Shift Point" for oceanic-to-neritic species dominance. The top two tintinnid species in each group showed distinct variations in body size. Additionally, multivariate biotic-abiotic statistical analyses revealed that temperature determined tintinnid species richness, while temperature, salinity, Si(OH)4, and Chl a determined tintinnid abundance. Our study provides a substantial foundation for recognizing the oceanic-to-neritic species shift of tintinnids in the China's marginal seas, and highlights the role of biotic-abiotic factors in driving biogeochemical fluxes and the potential response of microzooplankton to future climate change.

Full-depth vertical distribution of planktonic ciliates (Ciliophora) and a novel bio-index for indicating habitat suitability of tintinnid in the Arctic Ocean

Despite the planktonic ciliate importance in the microzooplankton compartment, their full-depth vertical distribution in the Arctic Ocean was poorly documented as well as the related variations in different water masses. The full-depth community structure of planktonic ciliates was investigated in the Arctic Ocean during summer 2021. The ciliate abundance and biomass decreased rapidly from 200 m to bottom. Five water masses were identified throughout the water column and each one exhibited a unique ciliate community structure. Aloricate ciliates were singled out as the dominant group with average abundance proportion to total ciliates at each depth >95%. Large (>30 μm) and small (10-20 μm) size-fractions of aloricate ciliates were abundant in shallow and deep waters, respectively, which revealed an anti-phase relationship in vertical distribution. Three new record tintinnid species were found during this survey. Pacific-origin species Salpingella sp.1 and Arctic endemic species Ptychocylis urnula occupied the top abundance proportion in the Pacific Summer Water (44.7%) and three water masses (≥38.7%, Mixed Layer Water, Remnant Winter Water, Atlantic-origin Water), respectively. The habitat suitability of tintinnid abundant species was characterised by the Bio-index revealing a distinct death-zone for each species. Variations in survival habitat of abundant tintinnids can be regarded as indicators for the future Arctic climate change. These results provide fundamental data on the microzooplankton response to the intrusion of Pacific waters into the Arctic Ocean upon its rapid warming.

Integrative taxonomy and molecular phylogeny of three poorly known tintinnine ciliates, with the establishment of a new genus (Protista; Ciliophora; Oligotrichea)

BACKGROUND

The taxonomic classification of the suborder Tintinnina Kofoid & Campbell, 1929, a species-rich group of planktonic ciliated protistans with a characteristic lorica, has long been ambiguous largely due to the lack of cytological and molecular data for most species. Tintinnopsis is the largest, most widespread, and most taxonomically complex genus within this group with about 170 species occurring in nearshore waters. Previous molecular phylogenetic studies have revealed that Tintinnopsis is polyphyletic.

RESULTS

Here we document the live morphology, infraciliature, gene sequences, and habitat characteristics of three poorly known tintinnine species, viz. Tintinnopsis karajacensis Brandt, 1896, Tintinnopsis gracilis Kofoid & Campbell, 1929, and Tintinnopsis tocantinensis Kofoid & Campbell, 1929, isolated from the coastal waters of China. Based on a unique cytological feature (i.e., an elongated ciliary tuft with densely arranged kinetids) in the former two species, Antetintinnopsis gen. nov. is erected with Antetintinnopsis hemispiralis (Yin, 1956) comb. nov. (original combination: Tintinnopsis hemispiralis Yin, 1956) designated as the type species. Moreover, A. karajacensis (Brandt, 1896) comb. nov. (original combination: Tintinnopsis karajacensis Brandt, 1896) and A. gracilis (Kofoid & Campbell, 1929) comb. nov. (original combination: Tintinnopsis gracilis Kofoid & Campbell, 1929) are placed in a highly supported clade that branches separately from Tintinnopsis clades in phylogenetic trees based on SSU rDNA and LSU rDNA sequence data, thus supporting the establishment of the new genus. One other species is assigned to Antetintinnopsis gen. nov., namely A. subacuta (Jörgensen, 1899) comb. nov. (original combination Tintinnopsis subacuta Jörgensen, 1899).

CONCLUSIONS

The findings of the phylogenetic analyses support the assertion that cytological characters are taxonomically informative for tintinnines. This study also contributes to the broadening of our understanding of the tintinnine biodiversity and evolution.

Spatial and seasonal variations in coastal water characteristics at Kalpakkam, western Bay of Bengal, Southeast India: a multivariate statistical approach

A study was carried out in the coastal waters of Kalpakkam with the objectives to evaluate the seasonality in hydrobiological parameters in surface and bottom waters, and assess the anthropogenic stress and monsoonal flux on a spatiotemporal scale. The study covered an area of approximately 100 km² in the coastal environment. Relatively high values for pH, temperature, and TP were observed during the post-monsoon (POM) season. The monsoon (MON) season was linked with TN, ammonia, and DO concentrations as all these parameters have shown increased values during this season due to freshwater input. The summer (SUM) season was characterized by salinity, turbidity, nitrate, phosphate, and silicate, indicating a true marine environmental condition for plankton production. Principal component analysis (PCA) and cluster analysis (CA) indicated the presence of distinct coastal water masses with respect to seasons and sampling regions. The spatial pattern indicated the distinctness of the coastal nearshore water (CNW) and coastal offshore water (COW) with respect to water quality. The CNW was more dynamic due to direct external influence as compared to the relatively stable COW environment. Similarly, the study region in the northern part, which is continuously exposed to the backwater inputs and tourism activities, was statistically different from the southern part.

Three redescriptions in Tintinnopsis (Protista: Ciliophora: Tintinnina) from coastal waters of China, with cytology and phylogenetic analyses based on ribosomal RNA genes

BACKGROUND

The taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.

RESULTS

Here, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) loci were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originated from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.

CONCLUSION

The redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary patterns and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.

A checklist of tintinnids (loricate ciliates) from the coastal zone of India

We report here a checklist of tintinnids (loricate ciliates) for the coastal zone of India. Based on available literature (1978 to 2017), a total of 25 stations were studied from 5 distinct areas of Indian coastal waters. A total of 151 species of 33 genera belonging to 14 families of tintinnids were documented. Diversity patterns of tintinnids were recorded higher along the west coast (30 genera and 106 species) than the east coast of India (20 genera and 93 species). Among tintinnids families, the Codonellidae (2 genera and 52 species, 20%) and the Tintinnidae (8 genera and 21 species, 19%) are the major contributors to the total tintinnids diversity in the Indian coastal zone.