Zooplankton diversity in Acre state, Amazon, Brazil: an overview of previous studies

This work assesses current knowledge of zooplankton biodiversity in aquatic ecosystems of the state of Acre (Brazil). A bibliographic survey was undertaken, showing that most of the reported studies have focused on zooplankton diversity and composition. Fifteen locations have been studied. There is still a scarcity of information concerning zooplankton populations in the Amazon region. To date, 170 species of planktonic rotifers have been recorded, distributed in 26 families and 38 genera, together with 18 species of cladocerans, distributed in 8 families and 18 genera, and 4 species of copepods in 2 families and 6 genera. The results indicate the need for further research concerning the biodiversity of this group of organisms at locations in the basins of the Purus and Juruá Rivers, especially in lotic ecosystems and littoral zones, given the present lack of information and the socioeconomic importance they play in the region.

Response of chlorophyll a to total nitrogen and total phosphorus concentrations in lotic ecosystems: a systematic review

Background Eutrophication of freshwater ecosystems resulting from nitrogen and phosphorus pollution is a major environmental stressor across the globe. In this systematic review, we compiled and synthesized literature on sestonic and benthic chlorophyll a (chl-a) responses to total nitrogen (TN) and total phosphorus (TP) concentrations in the water column in streams and rivers to provide a state-of-the-science summary of nutrient impacts on these endpoints. This review was motivated by the need for comprehensive information on stressor-response relationships for the most common nutrient and biotic response measures used by state-level environmental managers in the United States to assess eutrophication of lotic ecosystems and support environmental decision making. Methods Searches for peer-reviewed and non-peer-reviewed articles were conducted using bibliographic databases, specialist websites, and search engines. These returns were supplemented with citation mapping and requests for material from experts. Articles were screened for relevance using pre-determined eligibility criteria, and risk of bias was evaluated for each included article based on study type-specific criteria. Narrative summaries and meta-analysis were used to evaluate four primary stressor-response relationships: TN-benthic chl-a, TP-benthic chl-a, TN-sestonic chl-a, and TP-sestonic chl-a. Potential effects of modifying factors and study validity on review conclusions were assessed via sensitivity and sub-group analysis and meta-regression. Results Meta-analysis of 105 articles, representing 439 cause-effect pairs, showed that mean effect sizes of both benthic and sestonic chl-a responses to TN and TP were positive. Of the four stressor-response relationships examined, TP-sestonic chl-a had the most positive relationship, followed by TN-benthic chl-a, TN-sestonic chl-a, and TP-benthic chl-a. For individual U.S. states, mean effect sizes for the four stressor-response relationships were mostly positive, with a few exceptions. Chlorophyll measurement method had a moderately significant influence on mean effect size for TP-sestonic chl-a, with chl-a responding more strongly to TP if fluorometry versus spectrophotometry was used. Year of publication had a significant negative effect on mean effect size, as did mean nutrient concentration for both sestonic chl-a nutrient relationships. When the same study measured both TN and TP, chl-a tended to respond similarly to both nutrients. Sensitivity analysis indicated that conclusions are robust to studies with high risk of bias. Conclusions This systematic review confirms that nutrients consistently impact primary producer biomass in streams and rivers worldwide. It builds on previous literature syntheses evaluating chl-a responses to nutrient concentrations and confirms that benthic and sestonic chl-a respond positively to nutrients across a range of stream and river conditions, but also points to limits on these relationships (e.g., potential saturation at high nutrient concentrations). Lack of consistent reporting of contextual data limited our ability to examine how moderating factors influenced these stressor-response relationships. Overall, we provide nutrient managers responsible for protecting the quality of lotic ecosystems with a comprehensive evidence base for chl-a responses to TN and TP concentrations in the water column.

Big runs of little fish: First estimates of run size and exploitation in an amphidromous postlarvae fishery

Amphidromous Postlarvae Fisheries (APFs) constitute a globally-widespread and distinctive class of fishery that is largely unknown to fisheries science. APFs harvest ocean-to-river migrating fishes at smaller sizes and younger ages than any other class of fishery. No quantitative estimates of run size and exploitation exist, which are needed to evaluate APF sustainability. Migrating amphidromous fishes are vectors of marine nutrients to estuaries and rivers, and run size quantification is needed to reveal the magnitude of this ecosystem function. We present a novel adaptation of trapezoidal area under the curve (TAUC) methods, which we apply in a Caribbean case study to yield the first simultaneous estimates of an APF run size and harvest. Run size estimates ranged 7.3–9.4 million postlarvae (926–1,184 kg), and exploitation estimates (5.8–7.0%) indicated low harvest in the Río Grande de Arecibo, Puerto Rico. Our representative run size estimates reveal that amphidromous postlarvae transport hundreds of kilograms of biomass per month to an estuary and river, the first empirical evidence that amphidromous migrations are large-magnitude material subsidies of lotic ecosystems.

Effects of high-altitude reservoirs on the structure and function of lotic ecosystems: a case study in Italy

Alpine and pre-alpine lotic ecosystems are often remote and not affected by humans, which makes them some of the world’s most pristine ecosystems. However, their status is often altered by the presence of reservoirs that are built to fulfill agricultural needs and hydroelectric demands. These reservoirs also disrupt stream continuity and alter the magnitude, timing, and frequency of natural flows. The present work assessed how high-altitude reservoirs affect the riverine ecosystems focusing on the following: (i) the macroinvertebrate communities, (ii) the breakdown of organic matter, and (iii) the thermal regime. Stretches altered by high-altitude reservoirs had the best conditions for most macroinvertebrate families due to a more stable flow conditions. The breakdown rate of coarse particulate organic matter was not affected by high-altitude reservoirs but its availability was higher in altered compared to pristine stretches. The presence of hydroelectric power plants modified the stream thermal regime. Reservoirs mitigate the atmospheric influence on stream water temperature while run of the river plants strengthen it in the diverted stretches. Where both these alterations were present, the thermal regime of the stream was more similar to the natural ones compared to stretches subjected to only one kind of alteration. This research showed how river impoundment alters the structure of macroinvertebrate communities and the function of the downstream lotic ecosystems and can provide the basis to correctly guide management strategies for lotic ecosystems affected by hydrological alterations.

Aquatic insects, a tool for monitoring the health of riverine ecosystem, a case study of Killiyar, Thiruvananthapuram, Kerala, India

Aquatic insects are used as model organisms for assessing the health status of lenthic or lotic ecosystems. Biomonitoring using entomological indicators is one of the widely accepted tools to analyze the impacts of sewages in aquatic environment. The present study was aimed to assess the health status of a semi urban river system, Killiyar using entomological indicators. Season wise sampling of aquatic insects was done at four selected segments according to the rapid bioassessment protocol recommended by Environmental Protection Agency. The present study could identify 29 families of aquatic insects for screening the levels of pollution in Killiyar. Family Biotic Index (FBI) showed that there was a remarkable variation in water quality along the river. Hilsenhoff’s family biotic index obtained for river origin was in the range 4.40 - 5.02 indicating excellent water quality. High value of family biotic index, least occurrence of intolerant groups and dominance of tolerant taxa in the midstream and downstream segments showed that increased contamination of water by various sources. Immediate attention is needed to cease the degradation of this precious ecosystem. Keywords: Aquatic insects, Biomonitoring, Family Biotic Index, Killiyar, Water pollution

Effects of microbial conditioning and temperature on the leaf-litter shredding activity of Phylloicus sp.

Few studies try to explain the effects in tropical lotic ecosystems of an increase in water temperature on the shredding activity of invertebrate shredders, particularly in association with the quality of the leaf litter and the degree of litter conditioning. Therefore, the aims of this study were as follows: i) to better understand how this key invertebrate shredder group affects the decomposition of different species of leaf litter under gradual increases in temperature and microbial conditioning; and ii) to verify the possible consequences on leaf mass loss (LML). Three species of leaf litter were used in two experiments. In experiment I, the litters of three species (Protium spruceanum, Richeria grandis and Inga laurina) at three conditioning levels (1, 7, 14 days) were tested under five different temperatures (20, 22, 24, 26 and 28°C). In experiment II, the leaf litters of three species were used, without conditioning, under four temperatures (20, 22, 26 and 27°C). The shredding performed by Phylloicus sp. was largely dependent on the lignin and cellulose concentrations in each leaf species, independent of conditioning. The presence or absence of conditioning may cause the shredders to use different energy compensation strategies in response to the temperature increases.

Alien and translocated fish species in lotic ecosystems of Greece

Τα ενδημικά είδη ψαριών των εσωτερικών υδάτων και συγκεκριμένα αυτά των ρεόντων οικοσυστημάτων της Μεσογείου, συχνά επιβιώνουν σε ακραίες και δυναμικά μεταβαλλόμενες περιβαλλοντικές συνθήκες, ενώ πολλοί από τους πληθυσμούς τους ζουν κοντά στα φυσιολογικά τους όρια. Στην πραγματικότητα, ένας μεγάλος αριθμός ειδών υφίσταται ήδη έντονες πιέσεις λόγω πολλών ανθρωπογενών δραστηριοτήτων και οποιαδήποτε επιπρόσθετη ανθρωπογενή δραστηριότητα σε αυτά τα πλέον ευάλωτα οικοσυστήματα, όπως η εισαγωγή αλλόχθονων ειδών (ξενικών και αλλότοπων), έχει τη δυνατότητα να αυξήσει το μέγεθος των απειλών και να επιφέρει αλλαγές, σε διαφορετικές χωρικές κλίμακες. Ως εκ τούτου, ενώ η Μεσογείος θεωρείται ως ένα από τα σημαντικότερα και μεγαλύτερα «hotspot» βιοποικιλότητας των ψαριών των εσωτερικών υδάτων, είναι ταυτόχρονα μία από τις περιοχές με τις περισσότερες εισαγωγές ειδών σε παγκόσμιο επίπεδο. Η Ελλάδα αντίστοιχα, έχει μία από τις πλουσιότερες ιχθυοπανίδες του γλυκού νερού, σε σχέση με τις υπόλοιπες Ευρωπαϊκές χώρες, ενώ η εισαγωγή αλλόχθονων ψαριών στα ρέοντα συστήματα της αντιπροσωπεύει μια σχετικά πρόσφατη αλλά συνεχώς αυξανόμενη απειλή. Η απουσία ενός προγράμματος οργανωμένης παρακολούθησης τους σε συνδιασμό με τη έλλειψη ποιο-ποσοτικών δεδομένων, αποτελούν τα σημαντικότερα εμπόδια προς την σωστή ενημέρωση με έγκυρες και ολοκληρωμένες πληροφορίες που απαιτούνται για την λήψη μέτρων πρόληψης και διαχείρισης του προβλήματος στην Ελλάδα. Ωστόσο, βάσει των αποτελεσμάτων της παρούσας έρευνας, παρά την αυξανόμενη είσοδο των εισαγόμενων ειδών στα Μεσογειακά οικοσυστήματα, μόνο μια μικρή ομάδα ξενικών χωροκατακτητικών (εισβολικών) ψαριών έχει εισαχθεί στα ρέοντα οικοσυστήματα της χώρας. Ο υπόλοιπος μικρός αριθμός των ξενικών ειδών εντοπίζεται σε λίγες και μικρές λεκάνες, σχετικά απομονωμένες από το δίκτυο των μεγάλων λεκανών απορροής, διατηρώντας μικρούς πληθυσμούς, που συχνά δεν είναι ικανοί να αναπαραχθούν. Αντιθέτως, επί του παρόντος, η παρουσία των αλλότοπων ψαριών στα ελληνικά ποτάμια οικοσυστήματα είναι ένα σοβαρά παραμελημένο πρόβλημα, όπου συνήθως υποβαθμίζεται ως γεγονός, ενώ θα έπρεπε ήδη να θεωρείται ως ένα επιπρόσθετο και μάλιστα ύπουλο πρόβλημα που απειλεί την δομή και τις λειτουργίες των οικοσυστημάτων. Για τον σχεδιασμό κατάλληλων διαχείριστικών δράσεων εφαρμόστηκε ένα πλαίσιο ορισμού και ταξινόμησης των συναθροίσεων των αλλόχθονων ψαριών. Επιπρόσθετα πραγματοποιήθηκε η σύνδεση των συναθροίσεων με διάφορους περιφερειακούς, τοπικούς, βιοτικούς και αβιοτικούς περιβαλλοντικούς παράγοντες. Τα αποτελέσματα μπορούν να προτεραιοποιήσουν τις συναθροίσεις και τους κινδύνους τους, να συνδράμουν σε συγκεκριμένες δράσεις διαχείρισης που έπονται το στάδιο της εισαγωγής των ειδών. Επίσης, έχουν περαιτέρω την δυνατότητα να παρέχουν πολύτιμες πληροφορίες για ανεπηρέαστα οικοσυστημάτα από εισαγωγές αλλόχθονων ψαριών, όπου αποτελλούν υψηλή προτεραιότητα για την βιοποικιλότητα της χώρας. Η πρόβλεψη λοιπόν της πιθανής εγκατάστασης βιώσιμων πληθυσμών ξενικών ειδών ή/και της περαιτέρω εξάπλωσης τους, μπορεί να συμβάλει στη δημιουργία διαχειριστικών δράσεων, καθώς και στην πρόληψη μελλοντικών εισαγωγών. Για αυτό τον σκοπό, διερευνήθηκε επιπλέον η παρούσα κατανομή, η εγκατάσταση των πληθυσμών και η δυνητική εξάπλωση δύο ξενικών ψαριών, που έχουν ήδη εισαχθεί στα εσωτερικά ύδατα της χώρας. Οι δύο περιπτωσιολογικές μελέτες βασίστηκαν στην χρήση χωρικών κατανομών, δημογραφικών κριτηρίων, στην ένταση και συχνότητα εισαγωγών, στην αντιστοίχιση κλιματικών μεταβλητών και άλλων περιβαλλοντικών παραμέτρων. Τέλος, διερευνήθηκε η πιθανή χρήση ήδη εισαγμένων ειδών στην έρευνα, με στόχο την αξιοποίησή τους και ταυτόχρονα ένα ουσιαστικό μέτρο διαχείρισής των πληθυσμών τους. Συγκεκριμένα, χρησιμοποιήθηκαν άτομα από ένα πληθυσμό αλλότοπου ψαριού ως βιοδείκτες, με σκοπό την ανίχνευση και την αφθονία της μικροπλαστικής ρύπανσης στον Κηφισό ποταμό της Αττικής.

OPTIMALISASI PENGELOLAAN PERIKANAN DI DANAU GEGAS KABUPATEN MUSI RAWAS SUMATERA SELATAN

Danau Gegas (500 ha) merupakan danau buatan (waduk) dari pembendungan sungai gegas, diresmikan oleh Menteri Pekerjaan Umum pada 1987. Perubahan ekosistem yang mengalir menjadi ekosistem tergenang tentunya akan mempunyai dampak terhadap sumber daya perikanan. Permasalahan utama Danau gegas yaitu yang semula tujuan utama pembuatan danau buatan tersebut untuk keperluan irigasi ternyata tidak dapat berfungsi sebagaimana mestinya, pintu air tidak berfungsi sehingga sirkulasi air tidak berjalan dengan baik menyebabkan kualitas air menjadi jelek. Tujuan penelitian adalah mengoptimalkan peran perikanan di Danau gegas untuk kesejahteraan masyarakat yaitu dengan cara melakukan budidaya ikan yang sesuai dengan daya dukung perairan, penebaran ikan yang sesuai bagi jenis dan jumlah ikan yang ditebar, konservasi sumber daya ikan melalui penetapan suaka perikanan. Hasil penelitian menunjukkan bahwa daya dukung perairan untuk budidaya ikan pada keramba jaring apung adalah 20 ton/tahun, untuk jaring sekat 40 ton ikan/tahun, untuk penebaran benih ikan sebanyak 142.440 benih, penentuan suaka perikanan yang tepat adalah di inlet Gegas dan beberapa cekungan.Gegas Lake (500 ha) is an artificial lake (reservoir) from damming the gegas river, inaugurated by the Minister of Public Works in 1987. Changes in lotic ecosystems into lentic ecosystems will have an impact on fisheries resources. The main problem with the Gegas Lake is that it cannot function as an irrigation reservoir due to failure of water gate, so that the circulation of water does not work well causing worst water quality. The research objective is to optimize the fisheries function in Gegas Lake for the welfare of the community. For this reason, it is necessary to do fish culture in accordance with the carrying capacity of the waters and fish stocking and conservation through the establishment of fish reserves. The results showed that the carrying capacity of the waters for fish culture in floating cages and set net was 20 tons/year and 40 tons/year respectively. It was also suggested to conduct restocking as much as 120,000 juveniles. In addition, it was found that inlet and several concave areas were as correct places to conduct conservation activity.