ASSESSMENT OF EMERGENT AND FLOATING MACROPHYTES IN RELATION TO SOME PHYSICOCHEMICAL PARAMETERS OF WAYA POND, BAUCHI, NIGERIA

Emergent and floating macrophytes in relation to some physicochemical parameters were assessed in Waya pond, Bauchi. Water and macrophytes were sampled monthly between October 2019 to March 2020. Ten physicochemical parameters were measured and twelve macrophytes species recorded. The diversity index was 1.38, evenness (0.55) and abundance were 12 species. The site was polluted as all the values of dissolved oxygen (DO) were ˂ 5 mg/L, nitrogen ˃ 18 mg/L and pH ˂ 7 except for December. Pearson’s correlation coefficient revealed that DO correlated with Total Dissolved Solids (TDS) (r = 0.936, p˂0.01), Phosphate (r = 0.927, p˂0.01) and Nitrate (r = -0.953, p˂0.01). TDS correlated with Phosphate (r = 0.969, p˂0.01) and Nitrate (r = - 0.938, p˂0.01). The significant correlation between physicochemical parameters and macrophytes were: Nymphaea nouchali with DO (r = - 0.849, p˂0.05), TS (r = 0.88, p˂0.05). Panicum repens was negatively correlated with TDS, DO, TS, Phosphate but not Nitrates. Eichhornia crassipes, Nymphaea micrantha and Nymphaea lotus at p˂0.05 were negatively associated with TDS, DO, and Phosphate but positively with Nitrate. Nuphar lutea, Nelumbo nucifera and Echinochloa colona related positively with Turbidity. Nuphar lutea positively related with Nitrate but negative with DO, and TS. Typha latifolia with TS (r = - 0.871, p˂0.05). Potamogeton natans with phosphate (r = 0.927, p˂0.01). The state of water pollution in the study-area corresponded with low diversity, evenness and abundance of species. This puts biodiversity and sustainability at risk.

Specialization directs habitat selection responses to a top predator in semiaquatic but not aquatic taxa

Habitat selectivity has become an increasingly acknowledged mechanism shaping the structure of freshwater communities; however, most studies have focused on the effect of predators and competitors, neglecting habitat complexity and specialization. In this study, we examined the habitat selection of semiaquatic (amphibians: Bufonidae; odonates: Libellulidae) and aquatic organisms (true bugs: Notonectidae; diving beetles: Dytiscidae). From each family, we selected one habitat generalist species able to coexist with fish (Bufo bufo, Sympetrum sanguineum, Notonecta glauca, Dytiscus marginalis) and one species specialized in fishless habitats (Bufotes viridis, Sympetrum danae, Notonecta obliqua, Acilius sulcatus). In a mesocosm experiment, we quantified habitat selection decisions in response to the non-consumptive presence of fish (Carassius auratus) and vegetation structure mimicking different successional stages of aquatic habitats (no macrophytes; submerged and floating macrophytes; submerged, floating, and littoral-emergent macrophytes). No congruence between habitat specialists and generalists was observed, but a similar response to fish and vegetation structure defined both semiaquatic and aquatic organisms. While semiaquatic generalists did not distinguish between fish and fishless pools, specialists avoided fish-occupied pools and had a preferred vegetation structure. In aquatic taxa, predator presence affected habitat selection only in combination with vegetation structure, and all species preferred fishless pools with floating and submerged macrophytes. Fish presence triggered avoidance only in the generalist bug N. glauca. Our results highlight the significance of habitat selectivity for structuring freshwater ecosystems and illustrate how habitat selection responses to a top predator are dictated by specialization and life history.

Distribution and Diversity of Macrophytes in Relation to Some Physico-Chemical Factors in the Ketar River, Ziway Catchment, Ethiopia

Distribution and diversity of macrophytes in relation to some physico-chemical factors in the Ketar River were studied from December, 2017 to November, 2018. Physico-chemical parameters and macrophytes were collected from three stations along the river for eight months. Onsite measurements and laboratory work of physico-chemical was analyzed as recommended by APHA [31]. Macrophytes were collected manually using belt transect method. Except for pH and surface water temperatures, all the physico-chemical parameters measured showed no significant difference spatially. During the study period, sixteen macrophyte species belonged to fourteen families were identified. Among the identified macrophyte, 11 of them were emergent, while 3 were rooted with floating leaves and 2 free-floating. Free-floating macrophytes were shared the highest abundance followed by emergent. This research observed that the site (site 3) that was exposed to minimal human impact was rich in diversity and abundance of macrophytes. All the sites were dominated by emergent macrophytes that attained the highest relative frequency followed by rooted emergent species. Azolla nilotica and Pistia stratiotes were shared the highest abundance and were the dominant macrophyte with the relative frequency of 7.24% and density of 40.91%, and 7.93% and 26.54%, respectively. Under a favorable environment, nutrient loading from nearby creates more favorable conditions for the infestation of the invasive species (A. nilotica and P. stratiotes) to flourish and out-compete the other species of macrophyte. Therefore, anthropogenic activities that enhance nutrient addition to the River should be regulated.

Responses of Rotifer Community to Microhabitat Changes Caused by Summer-Concentrated Rainfall in a Shallow Reservoir, South Korea

Empirical studies suggest that the structural heterogeneity of aquatic ecosystem microhabitat is determined by the diversity and abundance of macrophytes. However, excessive accumulation of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes, resulting in a relatively simplified habitat structure. We hypothesized that heavy summer rainfall disrupts the growth of free-floating macrophytes covering much of the Jangcheok Reservoir’s water surface, thereby resulting in a more complex habitat structure by allowing development of a more diverse of macrophytic community. We divided long-term (2008–2017) monitoring data (rainfall, macrophytes, and rotifers) into two groups: Rainy and Dry years, corresponding to years with annual rainfall higher and lower than the total annual average, respectively. We found that summer densities of rotifers fell sharply in Rainy years, but increased continuously in Dry years. This trend resulted in greater autumn densities in Rainy relative to Dry years, which we attributed to changes in habitat related to differential macrophyte development. Moderate disturbance of the water surface caused by high summer rainfall can promote growth of submerged macrophytes by creating large areas of open water and therefore a more complex autumnal microhabitat structure, resulting in seasonal variations in rotifer community structures and populations. Moreover, a highly complex microhabitat structure restricts foraging activity of fish (i.e., Lepomis macrochirus) that prey on rotifers. Based on these findings, we suggest that summer-concentrated rainfall plays an important role in supporting the density and species diversity of rotifers.

Removal of ammoniacal nitrogen from municipal landfill leachate with floating Typha domingensis (Typhaceae)

A promising method for the treatment of effluents is the use of floating macrophytes. Ammoniacal nitrogen is a typical compound present in urban landfill leachates and its removal is important due its toxicity to several organisms. Therefore, the study evaluated Typha domingensis survival and nitrification potential artificially floating in domestic solid waste leachate. Plants were exposed for 35 days to leachate (100, 75 and 50 %) and to rainwater with N:P:K (control). Dissolved oxygen (DO) of the treatments was periodically measured, and ammoniacal nitrogen, nitrite and nitrate were analyzed before and after exposure. At the end of the experiment, plant survival rate was calculated. After two weeks, DO increased twice in the control, three times in 50 % leachate, four times in 75 % leachate, and eight times in 100 % leachate. At the end of the experiment, ammoniacal nitrogen was no longer detected, there was a significant reduction of nitrite, and a significant increase of nitrate in the treatments containing leachate. Plant survival was higher in those individuals exposed to 100 % leachate and decreased at lower leachate concentrations: 98 %, 94 %, 92 %, and 86 %. The study demonstrated that the ammoniacal nitrogen concentration of the leachate was not toxic to T. domingensis, and that it was efficient in the removal of this compound from the effluent, indicating that the species may be used artificially floating for the removal of this contaminant from domestic solid waste landfill leachate when in low concentrations.

An Exploration of Common Greenhouse Gas Emissions by the Cyanobiont of the Azolla–Nostoc Symbiosis and Clues as to Nod Factors in Cyanobacteria

Azolla is a genus of aquatic ferns that engages in a unique symbiosis with a cyanobiont that is resistant to cultivation. Azolla spp. are earmarked as a possible candidate to mitigate greenhouse gases, in particular, carbon dioxide. That opinion is underlined here in this paper to show the broader impact of Azolla spp. on greenhouse gas mitigation by revealing the enzyme catalogue in the Nostoc cyanobiont to be a poor contributor to climate change. First, regarding carbon assimilation, it was inferred that the carboxylation activity of the Rubisco enzyme of Azolla plants is able to quench carbon dioxide on par with other C3 plants and fellow aquatic free-floating macrophytes, with the cyanobiont contributing on average ~18% of the carboxylation load. Additionally, the author demonstrates here, using bioinformatics and past literature, that the Nostoc cyanobiont of Azolla does not contain nitric oxide reductase, a key enzyme that emanates nitrous oxide. In fact, all Nostoc species, both symbiotic and nonsymbiotic, are deficient in nitric oxide reductases. Furthermore, the Azolla cyanobiont is negative for methanogenic enzymes that use coenzyme conjugates to emit methane. With the absence of nitrous oxide and methane release, and the potential ability to convert ambient nitrous oxide into nitrogen gas, it is safe to say that the Azolla cyanobiont has a myriad of features that are poor contributors to climate change, which on top of carbon dioxide quenching by the Calvin cycle in Azolla plants, makes it an efficient holistic candidate to be developed as a force for climate change mitigation, especially in irrigated urea-fed rice fields. The author also shows that Nostoc cyanobionts are theoretically capable of Nod factor synthesis, similar to Rhizobia and some Frankia species, which is a new horizon to explore in the future.