Spatial and seasonal changes of As, F− and NO3− in a typical volcanic-sedimentary aquifer in Mexico: chemometric and multivariate analyses

Seasonal change in surface melt input and spatial controls on the distribution of subglacial water can cause considerable variability in the aqueous chemistry of subglacial waters. Much of this variability has been interpreted in terms of a single variable: water residence time, with slow flow assumed to correlate with greater mineral dissolution and oxidative weathering. We synthesize data from a range of glacier and ice sheet settings to show that this approach does not adequately describe presently available data. Instead, we propose that two independent variables control spatial and seasonal changes in aqueous chemistry in subglacial settings: atmospheric gas abundance and sediment supply abundance. Where atmospheric gases are abundant, carbonation weathering is responsible for most of the subglacial chemical activity; where they become limited, oxidation weathering becomes more dominant. Where freshly comminuted sediment is abundant, easily dissolved minerals, especially calcite, have proportionally more influence on subglacial hydrochemistry; where sediment supply is limited, silicate minerals and less reactive carbonate minerals will increase in relative influence. In most settings, simple metrics of the abundance of SO42- and Ca2+ in the subglacial waters can characterize these two variables. In the data we synthesize, neither variable consistently correlates to the inferred water residence time, nor do the variables consistently correlate with each other. Spatial data show that point locations and small catchments on the glacial bed differ substantially from the integrated composition found at glacial outlets. The varied response in the subglacial aqueous chemistry to changing water residence times suggests complex control by a broad range of glaciological factors that affect water routing and subglacial sediment generation.

Changes in the frequency of individual species, and in the species composition of the vegetation were monitored at monthly intervals at four stations on the shore of Lake Chilwa. The stations formed a transect from land to lake through the littoralTypha swamp. The relationships between seasonal changes in the frequency of individual species and fluctuations in water level were shown. Stand distance indices decreased from land to lake whilst species diversity decreased from land to the central swamp and then rose again on the lake edges. Seasonal changes in the vegetation were more pronounced on the landward edge, which was subjected to alternate wet and dry periods than in the vegetation of the lake edge. The reasons for these spatial and temporal changes are discussed. It is suggested that plant communities occurring in a fluctuating physical environment may behave differently with respect to diversity from those in which the environment is temporally stable.

Plant hormones coordinate monolignol biosynthesis with seasonal changes in Populus tomentosa

The main objective of this study was to statistically evaluate the significance of seasonal groundwater quality change and to provide an assessment on the spatial distribution of specific groundwater quality parameters. The studied area was the Mount Nif karstic aquifer system located in the southeast of the city of Izmir. Groundwater samples were collected at 57 sampling points in the rainy winter and dry summer seasons. Groundwater quality indicators of interest were electrical conductivity (EC), nitrate, chloride, sulfate, sodium, some heavy metals, and arsenic. Maps showing the spatial distributions and temporal changes of these parameters were created to further interpret spatial patterns and seasonal changes in groundwater quality. Furthermore, statistical tests were conducted to confirm whether the seasonal changes for each quality parameter were statistically significant. It was evident from the statistical tests that the seasonal changes in most groundwater quality parameters were statistically not significant. However, the increase in EC values and aluminum concentrations from winter to summer was found to be significant. Furthermore, a negative correlation between sampling elevation and groundwater quality was found. It was shown that with simple statistical testing, important conclusions can be drawn from limited monitoring data. It was concluded that less groundwater recharge in the dry period of the year does not always imply higher concentrations for all groundwater quality parameters because water circulation times, lithology, quality and extent of recharge, and land use patterns also play an important role on the alteration of groundwater quality.

SummaryTo quantify the major environmental drivers of stream bacterial population dynamics, we modelled temporal differences in stream bacterial communities to quantify community shifts, including those relating to cyclical seasonal variation and more sporadic bloom events. We applied Illumina MiSeq 16S rRNA bacterial gene sequencing of 892 stream biofilm samples, collected monthly for 36‐months from six streams. The streams were located a maximum of 118 km apart and drained three different catchment types (forest, urban and rural land uses). We identified repeatable seasonal patterns among bacterial taxa, allowing their separation into three ecological groupings, those following linear, bloom/trough and repeated, seasonal trends. Various physicochemical parameters (light, water and air temperature, pH, dissolved oxygen, nutrients) were linked to temporal community changes. Our models indicate that bloom events and seasonal episodes modify biofilm bacterial populations, suggesting that distinct microbial taxa thrive during these events including non‐cyanobacterial community members. These models could aid in determining how temporal environmental changes affect community assembly and guide the selection of appropriate statistical models to capture future community responses to environmental change.

In this study, we present results on seasonal and spatial changes in CDOM absorption and fluorescence (fCDOM) in a deep mountain lake (Salto Lake, Italy). A novel approach was used to describe the shape of CDOM absorption between 250-700 nm (distribution of the spectral slope, S(lambda)) and a new fluorescence ratio is used to distinguish between humic and amino acid-like components. Solar ultraviolet irradiance, dissolved organic carbon (DOC), DOM fluorescence and absorption measurements were analysed and compared to other physicochemical parameters. We show that in the UV-exposed mixed layer: (i) fluorescence by autochthonous amino acid-like CDOM, (ii) values of S(lambda) across UV-C and UV-B wavebands increased during the summer months, whereas (i) average molar absorption coefficient and (ii) fluorescence by allochthonous humic CDOM decreased. In the unexposed deep layer of the water column (and in the entire water column in winter), humic-like CDOM presented high values of molar absorption coefficients and low values of S(lambda). UV attenuation coefficients correlated with both chlorophyll a concentrations and CDOM absorption. In agreement with changes in CDOM, minimal values in UV attenuation were found in summer. The S(lambda) curve was used as a signature of the mixture between photobleached and algal-derived CDOM with respect to the unexposed chromophoric dissolved compounds in this thermal stratified lake. Furthermore, S(lambda) curves were useful to distinguish between low and high molecular weight CDOM.

The pro/antioxidant status of marine macrozoobentic organisms is being increasingly applied in environmental monitoring and conservation programs. The oxidative stress level in marine bivalves can provide valuable information not only on the health of the organisms and their populations, but also on the current state of habitats and ecosystems. The aim of the present study was to make the first comprehensive investigation of the seasonal changes in the antioxidant activity in different organs (gills, digestive gland and foot) of M. galloprovincialis from representative Bulgarian Black Sea coastal habitats. The lipid peroxidation and glutathione levels, as well as activities of the antioxidant enzymes catalase, superoxide dismutase, glutathion peroxidase, glutathion reductase, glucose-6-phosphate dehydrogenase and glutathione-S-transferase of the organs were measured spectrophotometrically. Our hypothesis was that enhanced environmental pressure during the summer season, induced by multiple factors (biogenic, abiogenic and anthropogenic) led to weakening of the antioxidant protection in mussels at the beginning of autumn. The reaction of the mussel organism to the multiple stress factors was specific for the target organ and the type of the biomarker. Significant differences were present in the activity of the antioxidant system in mussels from the northern and southern coastal locations. The seasonal changes in the pro/antioxidant status of mussels were primarily due to specific seasonal changes in factors concerning the marine environment at the concrete locality. Further research is obviously needed to confirm the present results and provide a more complete data of seasonal and spatial changes in the antioxidant defense system of mussels from the Bulgarian Black Sea coastal area and their implementation in biomonitoring programs.

Temporal and spatial changes of microbial community in an industrial effluent receiving area in Hangzhou Bay

Department of Invertebrate Zoology andHydrobiology, University of Lodz, Lodz, PolandSummaryThe Amur sleeper diet spectrum was investigated in addition toits spatial, seasonal and size-related changes, in order topredict which groups of native prey would be most affected bythis exotic predator that has rapidly invaded many Eastern andCentral European inland waters in recent decades. In total, 527Perccottus glenii individuals were collected in four sites in theWloclawski Reservoir (the Vistula River, Baltic basin, Po-land). Altogether 50 food categories were identified, includingcrustaceans, insects, molluscs, annelids, araneids, fishes andamphibians. Most of them were associated with aquaticvegetation, indicating that the Amur sleeper collects its preyfrom the submerged plants rather than directly from thebottom sediments. Amphipods and chironomid larvae, sup-plemented by zygopteran larvae and molluscs, composed themain forage base in all studied sites, although their importancewas varied. The diet composition differed among P. glenii size-groups. Significant variation was found in numeric abundanceof amphipods, chironomid larvae, fish and zygopteran larvae(Kruskal–Wallis P < 0.01). Seasonal changes in the diet werealso observed whereby in spring and summer, dipteran larvaeand amphipods were prevalent food items; the importance ofmolluscs and zygopteran larvae increased considerably inSeptember; and fish showed the highest occurrence in June,July and August. The broad diet spectrum of the Amur sleeperindicates that it is a non-selective, opportunistic predator andthat several taxonomic groups of native hydrofauna as well asmacroinvetebrates and fish may be affected by its presence.The highly flexible feeding strategy undoubtedly favours Amursleeper expansion in invaded watersheds.IntroductionMost definitions of invasive alien species underline theirnegative effects on native ecosystems and the threats that theirspread cause to local biological diversity. One of the possibleecological impacts of invasive fishes is alteration of trophicrelationships in aquatic communities that can be happen in atleast three different ways. First, non-native species mayincrease the amount of prey available to native predators.Second, the aliens can reduce food resources available tonative species through a dietary overlap. Finally, if the invasivefish is a predator, it can profoundly affect the populationdynamics of indigenous prey species (Moyle and Light, 1996;Simon and Townsend, 2003). The latter threat appears to bethe most drastic.The case of the Amur sleeper is among the most impressiverecent East-to-West invasions in European inland waters(Copp et al., 2005). Of Far East origin (mainly from AmurRiver system), it was first introduced into European areas ofRussia in 1912, and soon spread to the former Soviet Union(Reshetnikov, 2004). In the 1990s its rapid expansion was alsoobserved in the Vistula River system in Poland (Terlecki andPalka, 1999; Kostrzewa et al., 2004), along the Danube and itstributaries in Hungary (Harka, 1998), Slovakia (Kosˇcˇo et al.,2003), Serbia (Gergely and Tucakov, 2004; Hegedisˇ et al.,2007), Romania (Nalbant et al., 2004) and Bulgaria (Jurajdaet al., 2006).Perccottus glenii is a predator with morphological featuresenabling it to hunt a broad variety of aquatic organismsincluding relatively large prey items (Miller and Vasileva,2003). Its diet was studied mostly in its native range (Sinelni-kov, 1976) as well as some invaded ecosystems in Russia(Spanovskaya et al., 1964; Litvinov and OGorman, 1996;Reshetnikov, 2001, 2003, 2008). In all cases the species wasreported to be a voracious predator with a broad dietconstituting crustaceans (Cladocera, Copepoda, Malacostra-ca), larvae and insects (Ephemeroptera, Odonata, Hemiptera,Diptera, Trichoptera, Coleoptera), molluscs, fish, and evenlarvae of amphibians (frogs and newts) that are rarelyconsumed by other fish. Effects of the species predation onaquatic communities in small waterbodies in Russia werereported as deteriorative, as it was able to exhaust entire foodsupplies. Reshetnikov (2001, 2003) revealed that in smallwaterbodies the Amur sleeper depressed macroinvertebratepopulations as well as fishes, and that newts and frogs couldnot successfully reproduce due to predation pressure. As aresult, a negative correlation between the presence andabundance of P. glenii and the richness of aquatic specieswas observed. Long-term studies near Moscow (Spanovskayaet al., 1964) showed that the composition of consumed foodchanged along with the alterations caused to available prey inlocal communities. After the abrupt impoverishment of thelarge invertebrates fauna, the elimination of eggs, larvae andjuveniles of crucian carp and tadpoles in the P. glenii diet andcannibalistic behaviour was noted. This shows Amur sleeper tobe an effective switch-predator.It is expected that the recent rapid expansion of P. glenii inCentral European waters will cause a serious threat to localaquatic communities. Unfortunately, there are no data on itsfeeding habits in this region. Thus, the purpose of the presentstudy was to define the Amur sleeper diet spectrum, its spatial,seasonal and size related changes as well as to predict whichgroups of native prey would be most affected by the presenceof this exotic predator in the newly invaded locations in theexample of the Vistula River in Poland.

This study provides an opportunity to quantify the biogenic component of the carbon balance, its dynamics and relationship with environmental factors. This study is the first to evaluate the functioning of microbial communities in floodplain lakes in the middle reaches of the Ob River from the perspective of studying their metabolic activity in the context of seasonal and spatial environmental changes. The purpose of this work was to assess seasonal changes in the metabolic spectra of bacterial communities in water bodies of the Middle Ob floodplain. During the summer low water period (September 2023), winter low water period (snow period, March 2024) and spring flood (May 2024), functional diversity and quantitative microbiological characteristics of heterotrophic microbial communities in the surface and bottom layers of the water column of three floodplain lakes located in the vicinity of the TSU research station “Kaibasovo” (N 57.24569342272839, E 84.18459154598635), as well as the water of the Ob River itself, were studied. Functional diversity was determined using the multisubstrate testing method on 96-well Biolog Ecoplate test systems (USA) with calculation of the AWCD (average well-covered development) index. The TMC (total microbial count), obtained by direct counting of bacterial cells in a fluorescent-stained sample, was used as a quantitative characteristic. According to the nonparametric analysis of variance (Kruskal-Wallis ANOVA test, Median test), AWCD and TMC did not differ between lakes (p&gt;0.05). Seasonal changes were revealed for AWCD and TMC (see Fig. 1). AWCD correlated (Spearman rank correlations were used, p &lt; 0.05) with the consumption of amino acids (0.52), carbohydrates (0.54), amines (0.50) and oxycar-boxylic acids (0.62), TMC correlated with the consumption of carbohydrates (0.45) and polymers (0.63). The dynamics of AWCD were similar for the surface layer of all lakes, and did not show obvious patterns in the bottom layer. Throughout the year, higher TMC values were observed in the bottom layer, although this pattern was not observed for AWCD (see Fig. 1). This is due to the effect of ultraviolet radiation from the sun and the influence of allochthonous microflora on the current AWCD values. TMC in floodplain lakes increased during winter low water and had minimum values during the flood period. During the winter low water period, the AWCD and the consumption of most substrate groups are higher in the bottom layer. Seasonal differences in consumption of carboxylic acid phosphates (Kruskal-Wallis test: H (2, N = 18) = 10.36; p = 0.01; Median test: Chi-Square = 12.00; df = 2; p = 0.00) and polymers (Kruskal-Wallis test: H (2, N = 18) =7.18; p = 0.03; Median test: Chi-Square = 9.33; df = 2; p = 0.01) have been identified (see Fig. 2). A large number of correlations between the consumption of different groups of substrates, including within the surface and bottom layers, indicate the cosmopolitan nature and functional interchangeability of representatives of microbial communities. Moreover, during low water, when conditions are most favorable for the growth of microflora, the number of correlations was maximum (9 out of 15); during the freeze-up period it decreased significantly (4 out of 15), which may indicate a targeted growth of more specialized microflora. In May, the number of correlations increased again (5 out of 15). Seasonal changes in the functional and quantitative characteristics of microbial communities did not correspond to each other - the increase in the number of microorganisms did not cause an increase in functional diversity. The microflora suppression during flooding characterizes the demi-seasonal succession of the microbial community. Based on the data obtained, one can judge the functional cosmopolitanism and functional interchangeability of representatives of microbial communities of floodplain water bodies. The article contains 2 Figures, 12 References. To the team of the USI "System of Experimental Bases Located Along the Latitudinal Gradient" for assistance in organizing and conducting field work. The Authors declare no conflict of interest.

The distribution and availability of marine resources are directly affected by seasonal spatial changes in physical and oceanographic features. They are thus likely to influence maternal foraging provisioning patterns, efficiency, and subsequent pup growth rate of central place foragers such as otariid seals. While previous studies have documented foraging locations and diving activity of female otariids in relation to oceanographic features, few have focused on species characterised by a long pup-rearing period. The present study investigated seasonal changes in foraging parameters in relation to the following oceanographic features and maternal characteristics: foraging grounds (using satellite tags, geolocation, GIS and kernel estimation techniques), at-sea activity budget (using time-depth recorders), and the foraging success and diet of female subantarctic fur seals Arctocephalus tropicalis breeding on Amsterdam Island (southern Indian Ocean). The seals mainly exploited the subtropical front, but also exhibited large differences in seasonal distribution, from short trips in restricted foraging areas during summer to widely distributed foraging grounds during the winter. This is consistent with a seasonal shift in diet and an increasing proportion of time being dedicated to diving and resting. This increase in foraging trip duration throughout the season paralleled decreasing rates in maternal mass gain and pup growth, suggesting a decrease in food availability. During the summer, maternal mass gain rate and pup growth were related to foraging tactics (percent of time spent diving and in the core foraging area), whereas maternal characteristics such as body length were more important during the latter months of the pup-rearing period. However, no influence of age and thus no apparent advantage of female experience was detected in this study.

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m-3) was much lower than in the summer and autumn (410– 10 560 individuals m-3). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40–2010 individuals m-3) was much lower than in the summer and autumn (410– 10 560 individuals m-3). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.

Ammonia-oxidizing microorganisms (AOM) play crucial roles in the degradation of ammonia nitrogen in freshwater lakes. Hence, it is necessary to reveal the spatiotemporal dynamic changes of AOM in freshwater lakes. Here, we conducted a study on the spatial and temporal dynamic changes of AOM in different lake regions under gradient nutrient levels in Lake Taihu, and found that the abundance of AOM had significant spatial changes, while the seasonal changes had relatively little effect on the abundance of AOM. We also found that ammonia-oxidizing archaea (AOA) were adapted to freshwater habitats with low nutrient levels, while ammonia-oxidizing bacteria (AOB) and anaerobic ammonia-oxidizing bacteria (AAOB) had higher abundance in high nutrient level lake regions. Moreover, the amoA gene abundance of AOB was much higher than that of AOA, indicating that AOB was the dominant aerobic ammonia oxidizer in the water of Lake Taihu. In addition, temperature, pH and dissolved oxygen all had a positive effect on AOM, especially AOB; while C- and N-related physicochemical factors had a significant positive effect on AAOB, but exhibited a significant negative correlation with AOA. The community structure of AOM also had obvious spatial changes and Group I.1a, Nitrosomonas and Candidatus Brocadia fulgida were the dominant cluster of AOA, AOB and AAOB, respectively.

Benthic-pelagic coupling in the Southern California Bight: Relationships between sinking organic material, diatoms and benthic foraminifera