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Biofouling in freshwater and marine environments developed on man-made aquatic surfaces causes significant economic losses. Still, this problem is magnified when it comes to invasive species, such as the golden mussel. One of the alternatives to combat it is the use of antifouling solutions; however, the vast majority focus on solutions for the marine environment. In this same context, natural antifouling solutions from macrophytes have been reported as promising to combat estuarine biofouling; however, trials with freshwater organisms are still incipient. Thus, this study evaluated the performance of 25 macrophyte extracts in inhibiting the formation and/or eradication of bacterial biofilms, settlement of the golden mussel (Limnoperna fortunei), as well as its toxicity effect on three different non-target model organisms of three trophic levels. Among the 25 extracts, nine demonstrated ≥ 60% inhibition of biofilm formation, with only the extracts of Typha domingensis and Eichhornia crassipes having a biofilm inhibitory effect of ≥ 70% for bacterial isolates and ≥ 60% for multispecies biofilms. Planktonic growth had distinct responses, ranging from induction, inhibition, and no effect on growth. The T. domingensis extract showed quorum sensing inhibition (QSI) with a dose-dependent relationship, while the E. crassipes extract showed QSI only at a dilution of 1.2%. These same extracts prevented the golden mussel from attaching and showed safe concentrations of 35.35% for Pseudopediastrum boryanum and Daphnia magna and 70.71% for Pimephales promelas. This study highlights the biotechnological potential of macrophyte extracts as a sustainable and environmentally harmless alternative for the control of micro and macrofouling in freshwater environments., Competing Interests: Declarations. Ethical approval: According to Brazilian legislation (Law 11,794 of October 8, 2008), research with invertebrates does not require authorization from any ethics or animal welfare committee. The collection of invertebrates was approved by the Brazilian Agency SisBio (process no. 77095–1). The assay with P. promelas was approved by the Consejo Nacional del Ética Animal (CNEA) – Ata n° 17/11. Consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Co-author Ng Haig received research support from the National Council for Scientific and Technological Development – CNPq (Process 404233/2021–0), and co-author Grasiela Lopes Leães Pinho received research support from the Mixed Technical Commission of Salto Grande and Latitud (Uruguay Technological Laboratory Foundation – LATU)., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The yellow clam is a sand-burrowing bivalve that inhabits the dissipative beaches from southern Brazil to the north coast of Argentina. In the last decades, populations of this species have been impacted by mass mortality events, overfishing and other anthropogenic activities. The production of juveniles in captivity would allow feasibility studies to be carried out to restore the natural stock as well as the production in aquaculture systems. Given the scarcity of studies on the maintenance of this species in captivity, a culture system and a management protocol were developed and tested. Wild-caught clams (total length ≥50 mm) were used in a series of 14 day-long trials. Survival was higher in clams that were allowed to bury into the sand. A permanent ink marker covered with a thin layer of a quick-hardening adhesive proved to be a reliable method to tag clams. The maintenance of yellow clams in this system resulted in high survival and growth, increases in the condition factor and oocyte diameter, and a relative advancement of gonadal development.

A thermostable alkaline peptidase was purified from the processing waste of cobia (Rachycentron canadum) using bovine pancreatic trypsin inhibitor (BPTI) immobilized onto Sepharose. The purified enzyme had an apparent molecular mass of 24kDa by both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry. Its optimal temperature and pH were 50°C and 8.5, respectively. The enzyme was thermostable until 55°C and its activity was strongly inhibited by the classic trypsin inhibitors N-ρ-tosyl-l-lysine chloromethyl ketone (TLCK) and benzamidine. BPTI column allowed at least 15 assays without loss of efficacy. The purified enzyme was identified as a trypsin and the N-terminal amino acid sequence of this trypsin was IVGGYECTPHSQAHQVSLNSGYHFC, which was highly homologous to trypsin from cold water fish species. Using Nα-benzoyl-dl-arginine ρ-nitroanilide hydrochloride (BApNA) as substrate, the apparent km value of the purified trypsin was 0.38mM, kcat value was 3.14s(-1), and kcat/km was 8.26s(-1)mM(-1). The catalytic proficiency of the purified enzyme was 2.75×10(12)M(-1) showing higher affinity for the substrate at the transition state than other fish trypsin. The activation energy (AE) of the BApNA hydrolysis catalyzed by this enzyme was estimated to be 11.93kcalmol(-1) while the resulting rate enhancement of this reaction was found to be approximately in a range from 10(9) to 10(10)-fold evidencing its efficiency in comparison to other trypsin. This new purification strategy showed to be appropriate to obtain an alkaline peptidase from cobia processing waste with high purification degree. According with N-terminal homology and kinetic parameters, R. canadum trypsin may gathers desirable properties of psychrophilic and thermostable enzymes., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Ecological modeling has been used as a tool to estimate potential impacts caused by aquaculture to the surrounding environment. In this work, a mathematical model was applied to estimate the maximum amount of pink shrimp (Farfantepenaeus paulensis) culture units (3,100m2 pen enclosures) that could be installed at two shallow estuarine bays of Patos Lagoon (known as Coreia and Porto do Rei) with no significant effects on either water quality or viability of the culture system. To calibrate the model, information about the culture of Litopenaeus vannamei and F. paulensis as well as field data (influence of netting material, water current speed and nitrogen concentrations) were used. Under a bad scenario (water current velocity of 0.01m s-1 and a mesh clogging effect of 40%), it would be possible to install up to 29 pens at the Coreia bay, and 39 pens at the Porto do Rei bay. Results indicate that the model was useful in determining the maximum number of culture units that could be installed at these bays, and thus have the potential to become an important tool in the definition of environmental management strategies in relation to aquaculture development.

An alkaline peptidase was purified from the viscera of the silver mojarra (Diapterus rhombeus) in a three-step process: heat treatment, ammonium sulphate fractionation and molecular exclusion chromatography (Sephadex® G-75), with final specific activity 86-fold higher than the enzyme extract and yield of 22.1%. The purified enzyme had an estimated molecular mass of 26.5kDa and NH2-terminal amino acid sequence IVGGYECTMHSEAHE. Higher enzyme activity was observed at pH 8.5 and between 50 and 55°C. The enzyme was completely inactivated after 30min at 55°C and it was significantly more stable at alkaline pH. Km, Kcat and Kcat·Km(-1) values, using BApNA as substrate, were 0.266mM, 0.93s(-1) and 3.48mM(-1)s(-1), respectively. Enzyme activity increased in the presence of the ions (1mM) K(+), Li(+) and Ca(2+), but was inhibited by Fe(2+), Cd(2+), Cu(2+), Al(3+), Hg(2+), Zn(2+) and Pb(2+) as well as by the trypsin inhibitors TLCK and benzamidine., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The feasibility of a short-term ammonia toxicity test as an evaluation criterion for larval quality was assessed in three trials. In each one, Macrobrachium rosenbergii larvae originating from the same spawn were nutritionally differentiated in two groups by feeding them either a nutrient-rich (Artemia nauplii enriched for 24 h with n-3 highly unsaturated fatty acids (HUFA) and ascorbic acid (AA)) or a nutrient-poor diet (Artemia nauplii starved for 24 h). Throughout their development, larvae from both treatments were exposed during 24 h to six concentrations of total ammonia (NH(4)(+)+NH(3)) and a control (no ammonia added). Based on mortality rates, the median lethal concentration for 50% of the population (LC(50)) was estimated. As expected from earlier work, larvae fed the optimal diet presented higher n-3 HUFA and AA contents as well as higher growth and metamorphosis rates. From the moment the effect of diet quality was analytically detectable in the tissues of the larvae, the ammonia test was able to distinguish both groups of larvae. Differences in ammonia tolerance were observed as early as larval stage 4 and remained evident throughout larval development. The short-term ammonia toxicity test proved to be a valuable, sensitive and reproducible criterion for the establishment of larval quality.