Bacterial, phytoplankton, and viral dynamics of meromictic Lake Cadagno offer insights into the Proterozoic ocean microbial loop

Meromictic Lake Cadagno, with its permanent stratification and persistent microbial bloom within the anoxic chemocline, serves as an ancient ocean analogue. Although the lake has been studied for over 25 years, the absence of simultaneous study of the bacteria, phytoplankton, and viruses, together with primary and secondary productivity, has hindered a comprehensive understanding of its microbial food web. This study evaluated the identities, abundances, and productivity of microbes in the context of nutrient biogeochemical cycling across the stratified depths of Lake Cadagno. Photosynthetic pigments and chloroplast 16S rRNA gene phylogenies suggested high abundances of eukaryotic phytoplankton, primarily Chlorophyta, through the water column. Of these, a close relative of Ankyra judayi, a high-alpine adapted chlorophyte, peaked with oxygen in the mixolimnion, while Closteriopsis-related chlorophytes peaked in the chemocline and monimolimnion. Chromatium, a genus of anoxygenic phototrophic sulfur bacteria, dominated the chemocline along with Lentimicrobium, a genus of known fermenters whose abundance was newly reported in Lake Cadagno. Secondary production peaked in the chemocline, suggesting anoxygenic primary producers depended on heterotrophic nutrient remineralization. Virus-to-microbe ratios (VMR) peaked in the zone of high phytoplankton abundances, yet were at a minimum at the peak of Chromatium, dynamic trends that suggest viruses may play a role in the modulation of oxygenic and anoxygenic photo- and chemosynthesis in Lake Cadagno. Through the combined analysis of bacterial, eukaryotic, viral, and biogeochemical dynamics of Lake Cadagno, this study provides a new perspective on the biological and geochemical connections that comprised the food webs of the Proterozoic ocean.

Interactive Effects of Sediments and Urchins on Tropical Macroalgal Forests

Macroalgal forests are a prominent component of tropical seascapes providing food and shelter for many species whilst subsidising secondary productivity in coastal ecosystems. Monitoring and managing macroalgae requires an understanding of key processes that alter these assemblages, especially at the local scale. Here we consider how sediment depth/cover and abundance of the macroalgal grazing urchin Tripneustes gratilla (Linnaeus, 1758), influence variation in community composition and physical structure of macroalgal patches within the World Heritage listed Ningaloo Reef, Western Australia. Our study found high urchin densities in sites with lower sediment loads and that sediments, urchin abundance and seascape position combined, explained 32% of the spatial variation in macroalgal forest community composition. We also found a greater occurrence of Sargassopsis, Caulerpa, Sirophysalis and Hormophysa in the lagoon where sediment cover/depth was high. Canopy height and cover of canopy forming macroalgae was also greater where sediment loads were high and urchin abundance low. Macroalgal genera with a strong and robust thallus were found in sediment depths up to 6 cm as opposed to those with softer, fragile thalli that were found in sediments < 2 cm. Our results demonstrate that high densities of urchins and mobile sediments can have profound effects on the composition and structure of tropical macroalgal forests. Changes to macroalgal forest community composition and physical structure will have flow-on effects for ecological processes such as productivity and habitat use which can alter the ecosystem goods and services macroalgal forests provide.

THE PRIMARY AND SECONDARY PRODUCTIVITY OF THE SAVANNAS IN THE 'MIDDLE BELT' OF NIGERIA

No abstract

Do Dominant Ants Affect Secondary Productivity, Behavior and Diversity in a Guild of Woodland Ants?

The degree to which competition by dominant species shapes ecological communities remains a largely unresolved debate. In ants, unimodal dominance–richness relationships are common and suggest that dominant species, when very abundant, competitively exclude non-dominant species. However, few studies have investigated the underlying mechanisms by which dominant ants might affect coexistence and the maintenance of species richness. In this study, we first examined the relationship between the richness of non-dominant ant species and the abundance of a dominant ant species, Formica subsericea, among forest ant assemblages in the eastern US. This relationship was hump-shaped or not significant depending on the inclusion or exclusion of an influential observation. Moreover, we found only limited evidence that F. subsericea negatively affects the productivity or behavior of non-dominant ant species. For example, at the colony-level, the size and productivity of colonies of non-dominant ant species were not different when they were in close proximity to dominant ant nests than when they were away and, in fact, was associated with increased productivity in one species. Additionally, the number of foraging workers of only one non-dominant ant species was lower at food sources near than far from dominant F. subsericea nests, while the number of foragers of other species was not negatively affected. However, foraging activity of the non-dominant ant species was greater at night when F. subsericea was inactive, suggesting a potential mechanism by which some non-dominant species avoid interactions with competitively superior species. Gaining a mechanistic understanding of how patterns of community structure arise requires linking processes from colonies to communities. Our study suggests the negative effects of dominant ant species on non-dominant species may be offset by mechanisms promoting coexistence.

Seagrass Potential In Aisandami Village Wondama Bay and It’s Management Strategy

Seagrass ecosystem have primary and secondary productivity with great support to the abundance and diversity of fishes and it’s biota associations. Seagrass ecosystems are also as a coastal resources that have an important role of environmental services. Some community activities will directly or indirectly can have an impact on habitat degradation and biodiversity of seagrass ecosystems. The importance oto assess the potential of seagrass ecosystem and it’s biotas association is to know of sea grass’s role to provides of environmental services is the aim of this study. This research was conducted in the waters of Kampung Aisandami, Teluk Wondama Regency during June - July 2019. Data collection methodology was used is structured random methods quadrant transects at two observations to reveal data on seagrass community structure. The datas obtained were tabulated and displayed in tables and figures. Thalassia hemprichii and Enhalus acoroides were found at two observation sites. Another type found outside the observation transect is Halophila ovalis. E. acoroides seagrass species have a frequency value is 0.77 which shows that distribution of E. acoroides is wider than T. hemprichii which has a frequency is 0. 58. Both of station show that T. hemprichii has a frequency value of 0.7 where it indicates that distribution is wider compare with E. Acoroides. T hemprichii has the highest relative density at both observation stations. The status of seagrass of both stations is classified as poor or unhealthy with seagrass value ≥ 30-59.9%. The highest importance index is the T. hemprichii seagrass at both stations and has a higher role than the E. acoroides. The community-based management model is the a suitable model that can be used to developing coastal ecosystem management including seagrass ecosystems in this village.

Crocodilians and fisheries in the Philippines: revisiting Fittkau’s hypothesis

Crocodilians have been assumed to influence aquatic primary productivity and fishery yield. However, strong empirical evidence to support such claims is lacking. The long-standing assumption first hypothesized by Fittkau (1970), is that local fisheries (secondary productivity) in areas inhabited by crocodilians would be expected to improve. We tested this hypothesis at two locations in the Philippines, inhabited by the Philippine Crocodile (Crocodylus mindorensis) in Paghungawan Marsh in Siargao Island Protected Landscape & Seascape (SIPLAS), Jaboy, Pilar, Surigao Del Norte, and the Indo-Pacific Crocodile (Crocodylus porosus) in the Rio Tuba River, Bataraza, southern Palawan Island. Water chemistry parameters, with emphasis on nutrient (nitrate and phosphate) levels, were determined using using standard protocols. Catch-per-Unit Effort (CPUE) of gillnets in sites with crocodiles was compared with corresponding control sites without crocodiles. CPUE was higher in areas inhabited by crocodiles, but appeared not to be directly influenced by nutrient levels. Increased fish catches in areas inhabited by crocodiles might be attributed to several factors, such as reduced fishing pressure due to the presence of crocodiles which discouraged the local fishermen to fish intensively. Overall, while fish catch was higher in areas inhabited by crocodiles, it is too early to attribute this to the nutrient output from crocodiles due to several confounding factors. KEYWORDS: estuarine, fish catch, freshwater, nutrient

A report on freshwater tailless flea, Simocephalus vetulus from Haridwar, located in foothills of Shivalik Himalaya in Uttarakhand, India

The Cladocerans, commonly known as “Water fleas” form a primitive freshwater group of micro crustacean zooplankton of the freshwater ecosystem. They play an important role in the aquatic food chain and also contribute significantly to zooplankton dynamics and secondary productivity in freshwater ecosystems. The animals used in the present study were identified as Simocephalus vetulus with the help of identification keys described by various authors in the previous studies from other parts of India. In the present study, the occurrence of “freshwater tailless flea”, S. vetulus (Crustacea- cladocera) is reported for the first time from freshwater bodies in Haridwar, located in foothills of Shivalik Himalayan region in Uttarakhand. The presence of S. vetulus “tailless water flea” will be helpful as a lab model for the health status of aquatic bodies as well as environmental monitoring.