Aquatic Food Resources Research Articles

Cutthroat trout responses to increased light via conventional and alternative riparian buffers

Forested headwaters, particularly in the Pacific Northwest, USA, are typically heavily shaded by dense stands of riparian vegetation. Reduced riparian cover can occur from natural or anthropogenic events, resulting in increased light which can increase fish biomass by promoting in-stream food resources. We conducted a 5 y before-after-control-impact (BACI) study on 10 small streams in the Oregon Coast Range, USA, and investigated how changes to the magnitude of stream light, mediated by conventional and alternative riparian buffer configurations adjacent to upland timber harvest, changed Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) abundance, biomass, bioenergetics, diet composition, and the availability of aquatic food resources. Riparian buffer treatments reduced canopy cover as much as 34 % cover (98–99 % pre; 64–98 % post-treatment) and enhanced total available sunlight reaching the stream surface by 8–31 % relative to unharvested references that only changed by 3–4 %. In the first year following the treatments, young-of-year trout (YOY, age 0) densities changed by between +0.1 and +0.78 #/m2 in treatment streams while densities changed by –0.001 and +0.02 #/m2 at reference streams. Although change in YOY densities was positively correlated with change in stream light (rs=0.81, p=0.02), changes in basal resources (periphyton and macroinvertebrates) were both positive and negative and did not increase with change in stream light. Adult (age 1+) trout responses were mixed in the first year post-treatment, but changed by –0.14 to +0.24 #/m2 at treatment sites (–0.02 to –0.05 at reference sites) in the second year post-treatment, likely due to increased recruitment from the strong cohort of YOY in the first year. Bioenergetics analysis in one post-treatment year showed that adult trout did not experience greater summer growth (–0.003 to +0.0005 g g−1 d−1) or proportions of maximum consumption (0.18–0.25) in streams with more light than at reference streams (–0.001 and +0.001 g g−1 d−1, 0.19 and 0.23). Overall, while standing stock assessments suggest that fish showed some increases after experimental treatments that increased light, our data did not provide the clear mechanistic evidence for bottom-up drivers that was expected. The relationship between canopy removal and fish production is not always predictable in small headwater streams, and even though fish populations were generally resilient to riparian manipulation, evaluations of terrestrial food resources, the dynamic between canopy cover and light reaching the stream, and changes to temperature may lend valuable insight on the impacts to fish populations.

Aboriginal earth mounds and ENSO on the Calperum floodplain, Murray-Darling Basin, South Australia

This paper presents new data derived from pollen, starch and radiocarbon samples that were collected from six Aboriginal earth (oven) mounds and middens on the Calperum and Pike floodplains, Murray-Darling Basin (MDB), South Australia (SA). Analyses of these samples were undertaken in order to enhance our understanding about the Holocene lifeways of Aboriginal people living in this region. The results from these analyses, combined with published data about the mounds’ contents, relevant ethno-historical information and climate data, allow us to infer that Aboriginal people adopted, in this region, an innovative food production system about 3800 years ago. Further, we argue that the timing of the change suggests this was in response to adverse El Niño Southern Oscillation (ENSO) related weather patterns and consequently fluctuations in both terrestrial and aquatic food resources.

Aquatic food resources in tropical Africa: a comprehensive analysis

Aquatic food production holds great promise as a viable solution to tackle the pressing issue of meeting the protein requirements of the African populace. It plays a crucial role in food security and economic growth, especially in tropical Africa. With a fast-expanding population, there is a growing need for aquatic food sources to provide inexpensive protein and essential nutrients. Despite Africa’s vast aquatic food source supplies and the importance of aquatic food in healthy and sustainable diets, several challenges hinder its full exploitation in the tropical African environment. This study, therefore, aims to assess the existing state of aquatic food resources in Africa, examine the nutritional advantages associated with these foods, and identify the problems that hinder their maximal utilization. The findings highlight the differences in aquatic protein consumption across various countries, emphasizing the importance of considering local factors when formulating nutritional interventions and policies. The comparison between the supply of protein from aquatic sources and land animals across African nations revealed a consistent trend of lower availability of aquatic protein. Africa, in particular, had relatively lower per capita consumption values of animal protein. The continent’s average quantity of land animal food significantly surpassed the average aquatic food supply. This suggests a predominant reliance on land animal sources in African countries to meet dietary protein needs. This finding holds significant importance for policymakers, nutritionists, and stakeholders, highlighting the need for targeted strategies to improve protein accessibility in African countries. Moreover, it calls for attention to address any existing imbalances between the utilization of land and aquatic protein sources in the region.

Subsistence strategies in the Inner Congo Basin since the 14th century AD: the faunal remains from Nkile and Bolondo (DR Congo)

The faunal remains are described from Nkile and Bolondo, two archaeological sites in the equatorial rainforest of the Democratic Republic of Congo. Both river-side settlements, located in the Ruki-Tshuapa basin and dating to between the 14th century to the second half of the 20th century, show a heavy reliance on aquatic food resources. The animal remains show that fishing was a major subsistence activity, whereas hunting, slaughtering of domestic stock and harvesting of molluscs were less frequent activities. The contribution to the diet of the different animal taxa suggested by the zooarchaeological data is in line with recently published stable isotope results obtained on humans and animals from Bolondo. The type of fish, and in particular their reconstructed sizes, show that the major exploited fishing grounds were shallow waters that became accessible during the low water seasons (nowadays July-August and a minor season in March at both sites). The proportions of the exploited fish taxa are comparable to those marketed nowadays in larger urban centres. Juvenile fish, and to some extent, small crocodiles, were heavily exploited but it is argued that at the time this was still a sustainable activity that did not deplete the fauna as much as today since human populations were smaller and the fishing gear less effective.

Identification and environmental background of Chara remains in the Holocene sequence of Lake Peţea (NW Romania) and the possibilities of using the results in archaeobotany

The charophyte remains play an important role in the reconstruction of the hydrological characteristics (pH, water depth, stream flow, carbonate content, isotope geochemistry-water chemistry and temperature) of the former lake habitats. This is of particular importance in environmental historical studies, since the possibilities for obtaining aquatic food resources and the techniques and tools used are fundamentally influenced by these hydrological conditions. Our gyrogonite samples were recovered from the Holocene sequence of the thermalspring fed Lake Peţea NW Romania. The presence of the recovered Chara cf. hispida Linnaeus, 1753 gyrogonites marks the emergence of an oligotrophic shallow water lake system characterized by high dissolved Ca and Mg content and relatively poor plant cover in the Early Holocene. The results of previous malacological and ostracod studies also indicate the development of a shallow water lake with a muddy substrate and water temperatures above 18°C. As a warm-water lake, the local micro-environment was also home to many exploitable tree species. The charophyte remains that we recovered were from the Mesolithic level of the lake, so we were able to provide information on the hydrology of the lake for this period. Unfortunately, there have been no detailed archaeological investigations in the area to date revealing any potentially Mesolithic remains. Thus, no information is currently available on actual human occupation from the period in question.

Highly productive fishing in Lake Onega? New data on the subsistence basis of the Late Stone age populations in Russian Karelia

Recent excavations of the site of Fofanovo XIII (ca. 3500 to 3000 cal BC) on the western shore of Lake Onega, Russian Karelian, yielded evidence of production of Russian Karelian axes and adzes, as well as a rich faunal assemblage. Consisting mainly of unburnt bones, this assemblage represents a rare occurrence in Karelia and the neighboring regions of Russia and Finland, and sheds light on the subsistence of the Late Neolithic / Eneolithic populations of the Lake Onega. Fish bones overwhelmingly dominate, indicating a primary reliance on aquatic food resources, with the most common species being zander (over 80 %) and pike (ca. 9 %). In the specific natural conditions of the Early Subboreal in Lake Onega, zander was the species that could yield the maximal return of the invested effort, and this caused a very narrow specialization of fishing activities. The stable food supply provided by fishing favored tendencies towards complexity, which are evident through studies of the Russian Karelian industry. The analysis of the annual rings of zander vertebrae indicates that the site was in use during the snowless season. The identification of ringed seal, Atlantic sturgeon, and Wels catfish, which are not present in the lake nowadays, are also important results of the analysis.

Late Pleistocene–Holocene environmental and cultural changes in Primorye, southern Russian Far East: A review

This article presents an analytical review of the available palaeoenvironmental and archaeological records from the southern part (ca. 42°18′–45°30′N) of Primorye spanning the last ca. 21,000 years. The outlined climate and environmental history of the coastal and continental zones of southern Primorye, based mainly on vegetation reconstructions derived from the study of fossil pollen from sedimentary deposits from various archives, is compared with the archaeological cultural sequence of the region. This shows synchronicity between several phases of climate change and cultural transition, migration and changes in population numbers and/or subsistence strategies. The pronounced warming trend during the Early Holocene (Preboreal and Boreal stages) is associated with increasing numbers of long-term camp sites of the Late Palaeolithic hunter-gatherers and a growing importance of aquatic food resources. The Holocene maximum temperature and moisture conditions during the Atlantic stage were paralleled by the emergence and flourishing of the Neolithic Rudnaya, Vetka and Boisman cultures (ca. 7.7–5.5 14C ka BP/8.5–6.2 cal ka BP). The latter was a specialised maritime forager culture distributed along the Sea of Japan coast, which likely reflects climate conditions and sea water temperatures that promoted a broad spectrum of marine food resources. Towards the end of the Atlantic stage, sea levels decreased and transformed the coastal landscape of southern Primorye, which probably contributed to the decline of the Boisman culture. At the same time, the climate started to become cooler, which is likely related to the eastward migration of Zaisanovskaya culture groups from more continental (cooler) regions to milder southern Primorye. Continuous cooling during the Subboreal was accompanied by further immigrations of Zaisanovskaya people and an increase in millet cultivation, which probably occurred in the region between ca. 4.6–4.1 14C ka BP/5.3–4.6 cal ka BP. With the emergence of the Palaeometal Epoch cultures (ca. 3.6 14C ka BP/4.0 cal ka BP), food production diversified (growing number of cultivated crops, animal husbandry) and intensified, which probably decreased the people's dependence on climatic conditions unfavourable for food procurement. However, the maximum flourishing (ca. 2.8–2.6 14C ka BP/2.9–2.6 cal ka BP) of the Palaeometal Epoch Yankovskaya culture, represented by a maximum number of documented settlement sites in Primorye's prehistoric sequence, was likely related to a coeval short phase of climate amelioration with higher air and sea water temperatures and an increased sea level, which promoted agriculture and a higher productivity of coastal waters.

Large mammal hunting and use of aquatic food resources in the Early Palaeolithic (finds from Early Acheulean sites in the southern Azov Sea region)

Food sources and techniques of food procurement in the Early Palaeolithic have long been of interest to researchers. However, this is a complex and debatable problem; its solution is complicated by a lack of relevant archaeological data. This article describes and interprets archaeological evidence from a time transgressive series of sites belonging to the Taman Early Acheulean industry (Tamanian) in the southern Azov Sea region (~2.0–1.0 Ma). Analysis of the finds leads to the conclusion that makers of the Tamanian industry were hunters of large mammals, mainly southern elephants (Archidiskodon meridionalis tamanensis) and Caucasian elasmotherium (Elasmotherium caucasicum). Active hunting of these mammals as a way to procure meat emerged thanks to the particular environmental conditions of the southern Azov region in the Lower Pleistocene and the cognitive capabilities of prehistoric people. A specific strategy was devised and applied, i.e. hunting inside calderas of mud volcanoes that were present in numbers across the region. People took into consideration the behaviour of elephants and elasmotherium which came to calderas in order to drink or ‘take a bath’ in volcanic muds. It allowed prehistoric people to effortlessly hunt animals, which were immobilized in spongy mud, and to procure substantial meat supplies. Alongside hunting of large mammals, the makers of the Tamanian industry engaged extensively in a special form of gathering, i.e. beach gathering of high-protein food like shellfish, carcasses of sea animals, and fish. This reliable source of nutrition likely was one of the main reasons why the Tamanian sites were located on beaches adjacent to coastal lagoons and estuaries.

Food web reconstruction through isotopic compositions of fossil faeces: Insights into the ecology of a late Barremian freshwater ecosystem (Las Hoyas, Cuenca, Spain)

A total of 54 coprolites with different morphologies from the Konservat-Lagerstätte of Las Hoyas (upper Barremian, Cuenca, Spain) were analysed for stable isotopes (δ15N and δ13Corg) to examine the food-web structure of this ancient wetland. The Las Hoyas wetland exhibited wetter and drier periods that indicated water table oscillations. Differences in the δ15N values of coprolites collected from wetter and drier facies were probably due to different baseline δ15N values during the dry periods (higher) compared to those of the wetter periods. The δ13Corg values indicated that aquatic food resources were the most commonly used by the animals from Las Hoyas. Assuming a Trophic Enrichment Factor (TEF) of + 2.5 ‰, three trophic levels were established for the coprolite association. All the specimens of circular, ellipsoidal, elongated, and rosary morphotypes fell into the same trophic level, whereas other morphotypes (cylinder, irregular, and thin lace) exhibited a wide range of δ15N values and the highest % N concentrations. The covariation between δ15N and δ13Corg values describe a wide spectrum of values across the middle and upper part of the ecosystem's food web structure, suggesting that the Las Hoyas ecosystem hosted specialist feeders and omnivorous and/or opportunistic feeders, the latter being the majority. The variation of δ15N values within the specimens of some morphotypes showed that the larger coprolites do not exhibit any correspondence between the faecal size and δ15N values.

Ecosystem change and population declines in gulls: Shifting baseline considerations for assessing ecological integrity of protected areas

In Lake Superior's Pukaskwa National Park (PNP) in northern Ontario, Canada, herring gull (Larus argentatus) population size is used as an indicator of ecological integrity. Since the 1970s, gull populations have declined by 70% suggesting deteriorating park conditions. However, most other rated park indicators show stable or positive trends. Here, we focus on reconciling these seemingly disparate trends through a better understanding of factors regulating PNP gull populations. Lake-wide declines in surface-schooling prey fish may be limiting aquatic food resources for PNP gulls. To investigate this, we examined gull population trends in different parts of the park in the context of food availability. Gull diets were assessed using regurgitated pellets, egg stable isotopes (nitrogen, carbon) and fatty acids. Population declines were more severe in southern PNP compared to northern PNP and inter-region differences in bird diets likely contributed to these population trends. Gulls in the south relied to a greater extent on dwindling aquatic food resources, i.e., prey fish, while birds in northern PNP supplemented their diets with anthropogenic foods, i.e., garbage. Recognizing that regional declines in aquatic food availability have occurred across eastern Lake Superior is important for the interpretation of PNP gull population trends. Wide-scale ecological changes affecting PNP suggest that factors limiting PNP's herring gull population are not park-specific but, instead, reflect broader ecosystem-wide changes. Defining an appropriate threshold based on current knowledge of ecological conditions on Lake Superior is critical for using herring gull populations as an indicator of park ecological integrity.

Crab-fishing by chimpanzees in the Nimba Mountains, Guinea

The significance of aquatic food resources for hominins is poorly understood, despite evidence of consumption as early as 1.95 million years ago (Ma). Here we present the first evidence of a non-human ape habitually catching and consuming aquatic crabs. Chimpanzees (Pan troglodytes verus) in the rainforest of the Nimba Mountains (Guinea) consumed freshwater crabs year-round, irrespective of rainfall or ripe fruit availability. Parties of females and offspring fished for crabs more than predicted and for longer durations than adult males. Across months, crab-fishing was negatively correlated with ant-dipping, suggesting a similar nutritional role. These findings contribute to our understanding of aquatic faunivory among hominins. First, aquatic faunivory can occur in closed forests in addition to open wetlands. Second, aquatic fauna could have been a staple part of some hominin diets, rather than merely a fallback food. Third, the habitual consumption of aquatic fauna could have been especially important for females and their immature offspring. In addition to providing small amounts of essential fatty acids, crabs might also be eaten for their micronutrients such as sodium and calcium, especially by females and young individuals who may have limited access to meat.

Seasonal bat activity related to insect emergence at three temperate lakes.

Knowledge of aquatic food resources entering terrestrial systems is important for food web studies and conservation planning. Bats, among other terrestrial consumers, often profit from aquatic insect emergence and their activity might be closely related to such events. However, there is a lack of studies which monitor bat activity simultaneously with aquatic insect emergence, especially from lakes. Thus, our aim was to understand the relationship between insect emergence and bat activity, and investigate whether there is a general spatial or seasonal pattern at lakeshores. We assessed whole‐night bat activity using acoustic monitoring and caught emerging and aerial flying insects at three different lakes through three seasons. We predicted that insect availability and seasonality explain the variation in bat activity, independent of the lake size and characteristics. Spatial (between lakes) differences of bat activity were stronger than temporal (seasonal) differences. Bat activity did not always correlate to insect emergence, probably because other factors, such as habitat characteristics, or bats’ energy requirements, play an important role as well. Aerial flying insects explained bat activity better than the emerged aquatic insects in the lake with lowest insect emergence. Bats were active throughout the night with some activity peaks, and the pattern of their activity also differed among lakes and seasons. Lakes are important habitats for bats, as they support diverse bat communities and activity throughout the night and the year when bats are active. Our study highlights that there are spatial and temporal differences in bat activity and its hourly nocturnal pattern, that should be considered when investigating aquatic–terrestrial interactions or designing conservation and monitoring plans.

Evaluation of organochlorine and organophosphorus pesticides residues in the sediment and muscles of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) fish from a River Nile Canal, Egypt

The paper reports the levels of multi-pesticide residues in the sediment and fish (Oreochromis niloticus) muscle collected from Bahr Shebeen Canal (BSC), a River Nile Canal, from September 2014 to December 2015. Samples were analysed using capillary GC chromatography, and average pesticide residue concentrations were determined. The results indicated the presence of different types of organophosphorus (OPPs) and organochlorine (OCPs) pesticides in varying degrees. Both types of residue in the sediment samples were higher than in fish muscle. The spatial and seasonal variations of OPPs and OCPs levels in sediment and fish muscle are discussed. It was found that these levels were higher than those detected from other Egyptian localities and also higher than the international permissible limits. Therefore, it is recommended to monitor the pesticide residues continuously in this, and similar, water resources to ensure the protection of the aquatic food resources.

Ontogenetic shifts in terrestrial reliance of stream-dwelling brown trout

<p>This study focuses on terrestrial reliance of brown trout (<em>Salmo trutta</em>) and compared it to the potential prey available (macrozoobenthos and drifting invertebrates) in three temperate rivers (Galicia, NW Spain), with special emphasis on variations in terrestrial energy intake through the ontogeny of brown trout. Additionally, we paid particular attention to individual variation of terrestrial resource use within and between age classes. Prey items were grouped in four categories: i) aquatic invertebrates; ii) imagoes of aquatic invertebrates; iii) terrestrial invertebrates; and iv) fish prey. Next, energy composition was measured according to dry weight-energy equations for each individual in line with above-mentioned prey categories. Our findings illustrate that terrestrial invertebrates appeared to be scarce in the environment, whereas aquatic food resources were rather abundant and accessible. The use of terrestrial invertebrates tended to increase with age, but with a high degree of inter-individual variation in resource use. In fact, the individual reliance of brown trout on terrestrial invertebrates may vary considerably (between 0% and 76.9%). Besides, the frequency of terrestrial foragers, <em>i.e</em>., individuals with terrestrial invertebrates in their stomachs, increased with age, except in one population which had the maximum value in the age-2 class. The acquisition of terrestrial invertebrates thus appears to be a process strongly dependent upon the actual food availability in the environment, but with a high degree of individual variance in resource use within the same age class. Finally, we discuss that terrestrial invertebrates may largely contribute to cover the energy intake of the species, highlighting the interface between terrestrial and aquatic ecosystems, and thereby the importance of riparian canopy cover as a key factor for food supply of stream-dwelling salmonids species.</p>

Responses of riparian tetragnathid spiders to wildfire in forested ecosystems of the California Mediterranean climate region, USA

Mediterranean ecosystems of California are characterized by high interannual variability in precipitation and susceptibility to frequent high-severity wildfires. Variability in precipitation and fire severity are likely to become more pronounced because of climate change, but their relative effects on linked aquatic–terrestrial components of Mediterranean ecosystems have received limited attention. We investigated the effects of wildfire on riparian spiders of the family Tetragnathidae, which are common shoreline consumers that can be highly reliant on aquatic food resources in stream ecosystems. From 2011–2012, we assessed stream geomorphology; density and community composition of aquatic benthic macroinvertebrates; and density, Hg body loads, trophic position (TP), and reliance on aquatically derived energy (based on naturally abundant C and N isotopes) of tetragnathid spiders in study sections of 12 paired stream reaches in Yosemite National Park. The riparian zone of one member of each pair had experienced a high-severity wildfire, whereas the riparian zone of its counterpart had experienced a low-severity fire. After the 2013 Rim Fire, we resurveyed a subset of these variables in study sections of 4 reaches by means of a paired before-after–control-impact design. We also explored how reach- and catchment-scale variability might affect spider density and trophic dynamics. Differences in spider responses between paired sections were not statistically significant, but model-selection results suggested that variability in benthic invertebrate density, catchment-scale fire frequency, and precipitation were important drivers of spider density and TP. The consistent signal of precipitation across multiple spider responses suggests that climate variability could have greater effects on aquatic–terrestrial ecological linkages than the influence of fire alone.

Dietary freshwater reservoir effects and the radiocarbon ages of prehistoric human bones from Zvejnieki, Latvia

Aquatic food resources (fish and molluscs) were exploited intensively at Riņņukalns, a Neolithic freshwater shell midden at the outlet of Lake Burtnieks, north-eastern Latvia. Stable isotope data (δ15N and δ13C) from a rich fishbone assemblage and a wide range of terrestrial species complement published results on faunal samples from the famous prehistoric cemetery and settlement at Zvejnieki, on the same lake. Stable isotope data show that freshwater food resources made substantial but varying contributions to human diets at Zvejnieki and Riņņukalns throughout the Mesolithic and Neolithic. Our research has also shown significant radiocarbon freshwater reservoir effects (FRE) in aquatic species from Lake Burtnieks, which would presumably have affected the radiocarbon ages of prehistoric human remains, and may explain some apparent anomalies in published dates from Zvejnieki burials.We present new radiocarbon and stable isotope results from a multiple burial at Zvejnieki, of five contemporaneous individuals, whose remains are being re-examined to assess evidence of interpersonal violence. Contrary to earlier interpretations, our data show that differences between individuals in the amount of fish consumed would account for the 300-year spread in their radiocarbon ages, given the isotope data and our estimate of the effective FRE in local fish. Our FRE-corrected calibrated dates for these five individuals are therefore compatible with a single burial date. We propose that these models can be used to correct the calibrated radiocarbon ages of other Zvejnieki burials for dietary FRE, provided that the individuals concerned consumed mainly local resources. The same methodology can also be applied elsewhere, as long as local isotopic and FRE values are well understood, and values for terrestrial and aquatic species are sufficiently different.

Distribution and trophic dynamics of riparian tetragnathid spiders in a large river system

Development and agriculture are increasingly encroaching into riparian areas, with largely unknown effects on nearshore arthropods, which are important components of linked aquatic–terrestrial food webs. To assess the environmental determinants of the distribution and trophic dynamics of riparian spiders of the family Tetragnathidae, we characterised riparian habitat, collected emergent aquatic insects, and surveyed spiders in developed and rural landscapes of the Scioto River system, Ohio, USA, which provided a range of riparian land cover, nearshore vegetation types and habitat complexity. We also estimated the trophic position (TP) of Tetragnathidae and the proportion of energetic and nutritional subsidies derived from benthic algae (EBA) using naturally abundant carbon (C) and nitrogen (N) stable isotopes. Model-selection results revealed that tetragnathid spider density (1.57–3.80individualsm–1) was more sensitive to differences in overhanging vegetation than to those in aquatic food resources (i.e. emergent aquatic insects). Tetragnathidae TP, which averaged 3.16 across all 12 study reaches (range: 2.35–3.98), was largely driven by canopy density, shoreline shape, percentage overhanging vegetation and emergent-insect density. Emergent-insect density was the strongest driver of tetragnathid spider EBA (0.04–0.54, µ=0.24). Our study reinforced the notion that riparian spiders ecologically link aquatic and terrestrial ecosystems. In particular, our results further current understanding of the mechanisms affecting riparian spider distribution and trophic dynamics, particularly in the context of larger stream and river systems, given that the propensity of related research has occurred in small streams.

Occurrence, Species, and Organ Differences in Bioaccumulation Patterns of Phthalate Esters in Municipal Domestic Water Supply Lakes in Ibadan, Nigeria

The occurrence of phthalate esters (PE) was examined in biota, ambient water, and sediments of two man-made lakes (Asejire and Eleyele) in southwestern Nigeria. Five fish species (Tilapia zillii, Hepsetus odoe, Parachanna obscura, Chrysichthys nigrodigitatus, and Mormyrus rume) were analyzed for PE levels and used for calculating bioconcentration factors (BCF) and biota–sediment accumulation factors (BSAF). In addition, measured PE levels were thereafter used to calculate the phthalate pollution index (PPI) in biota and the environment. At both lakes, all sampled species had k-factor > 1, showing apparently normal growth and health condition. Higher PE levels were found in sediments compared with water at both lakes, with a pattern showing that di(2-ethylhexyl) phthalate (DEHP) was predominant PE. While there were no unique patterns of PE concentrations in both lakes, differences were observed in organ concentration patterns that were evident at both lakes. For T. zillii, the BSAF was higher for dibutyl phthalate (DBP) compared to diethyl phthalate (DEP) and lowest for DEHP. The concentration pattern demonstrated that DBP concentrated more in gills (BCF: 6.7), while DEHP concentrated more in liver (BCF: 15.2) of T. zillii at Asejire. At Eleyele, T. zillii liver and gills concentrated less DEP and DEHP. The PPI value was significantly higher in sediment with respective values of 0.27 and 0.44 at Asejire and Eleyele lakes compared with water with respective values of 0.1 and 0.18 at Asejire and Eleyele lakes. Overall, our findings suggest a broader environmental and human health implication of high PE levels in these lakes, since they provide vast water volumes that are used for municipal domestic water supply. Further, these lakes support intense artisanal fisheries, representing significant sources of aquatic food resources for neighboring communities.

Environmental occurrence and biota concentration of phthalate esters in Epe and Lagos Lagoons, Nigeria

The high global occurrence of phthalates in different environmental matrixes has resulted in the detection of their metabolites in human urine, blood, and breast milk, indicating a widespread human exposure. In addition, the notorious endocrine disrupting effects of phthalates have shown that they mimic or antagonize the action of endogenous hormones, consequently producing adverse effects on reproduction, growth and development. Herein, we have studied the occurrence of phthalate esters (PEs) in water, sediment and biota of two lagoons (Epe and Lagos) in Nigeria. Two fish species (Tilapia guineensis, and Chrysichthys nigrodigitatus) and a crustacean (the African river prawn - Macrobrachium vollenhovenii) were analyzed for PEs levels using a HPLC method and the derived values were used for calculating bioconcentration factor (BCF), biota-sediment accumulation factor (BSAF) and phthalate pollution index (PPI) in the biota and environment. We observed that the growth and health condition of the fish species were normal with a k-factor of >1. Sediment PE levels were compared with water, at both lagoons showing concentration pattern that is characterized as DEHP = DEP > DBP. We observed that DBP was the predominant compound in T. guineensis, C. nigrodigitatus and African prawn, at both lagoons, showing organ-specific differences in bioconcentration (BCF and BSAF) patterns in the fish species. While there were no observed consistency in the pattern of PE concentration in fish organs, elevated DBP levels in different fish organs may be related to fish habitat and degradation level of phthalates. Low concentration of DEHP, compared with DBP and DEP, was measured in fish organs and whole prawn body. The BSAF values for DEHP were lowest, and highest for DBP for all species at both lagoons, and DEHP easily accumulated more in the sediment (sediment PPI = 0.28 and 0.16 for Epe and Lagos lagoon, respectively). Overall, our findings suggest a broader environmental and human health implication of the high PE levels in these lagoons since they represent significant sources of aquatic food resources for the neighboring communities.

Inter- and intraspecies variability in stable isotope ratio values of archaeological freshwater fish remains from Switzerland (11th–19th centuries AD)

This paper presents carbon and nitrogen isotopic results from several Swiss freshwater fish (Esox lucius, Perca fluviatilis, Barbus barbus, Rutilus rutilus and other Cyprinidae) in order to provide information about their trophic level, feeding habits and provenance.Freshwater fish remains are regularly recovered from archaeological contexts in Switzerland, which attests to the importance of these aquatic food resources to past communities. However, it can be difficult to determine the effect of freshwater fish consumption in human bone isotope signatures by stable isotope ratio analysis. Therefore, an establishment of baseline isotope signatures of freshwater fish by region and time is necessary. Additionally, freshwater fish isotope analysis can serve as a backdrop for research on former aquatic isotopic ecology.We measured carbon and nitrogen isotope ratios of 140 freshwater fish bone samples from sites dating between the 11th and 19th centuries AD. Suitable C:N ratios (2·9–3·6) were obtained from 56 of the samples, a rather low success rate that may be the result of diagenetic contamination and insufficient sample weight (<20 mg). A high inter- and intraspecies variability of freshwater fish isotope signature was observed. The δ15N results indicate a size and age-related trophic level effect. Heterogeneous carbon isotope signatures from samples from the same site could indicate spatial variation in isotope values within a single ecosystem or alternatively represent the use of different fishing grounds.