Environmental Tradeoffs between Nutrient Recycling and Greenhouse Gases Emissions in an Integrated Aquaculture-Agriculture System.

The unlimited nitrogen (N) availability that has characterized crop production in the last few decades is accompanied by environmental burdens, including the greenhouse gas (GHG) emissions associated with fertilizer production, post-application nitrate (NO3-) pollution of water bodies, and emissions of reactive gaseous N forms into the atmosphere. Here, we quantified the environmental tradeoffs of replacing mineral N fertilizer with NO3- and ammonium (NH4+) originating from effluent water of aquaculture in a cucumber (Cucumis sativus) cultivation system. While the yield, nitrogen use efficiency (NUE), and NO3- leaching were similar between the cucumbers fertilized and irrigated (fertigated) by aquaculture effluent water containing 100 mg of NO3--N L-1 (AN), by aquaculture effluent water supplemented with NH4+ (AN+), or by tap water with NO3- and NH4+ added (FN+), there were significant differences in the nitrous oxide (N2O) emissions between the systems. The N2O emissions peaked after each irrigation event followed by an exponential decline. The cumulative N2O emissions were between 60 and 600 g N2O-N ha-1, smaller than predicted based on a fertilizer application rate of 600 kg N ha-1 and were in the order AN+ ≫ FN+ > AN.

Proteomic analysis of early-stage embryos: implications for egg quality in hapuku (Polyprion oxygeneios).

In order to develop biomarkers that may help predict the egg quality of captive hapuku (Polyprion oxygeneios) and provide potential avenues for its manipulation, the present study (1) sequenced the proteome of early-stage embryos using isobaric tag for relative and absolute quantification analysis, and (2) aimed to establish the predictive value of the abundance of identified proteins with regard to egg quality through regression analysis. Egg quality was determined for eight different egg batches by blastomere symmetry scores. In total, 121 proteins were identified and assigned to one of nine major groups according to their function/pathway. A mixed-effects model analysis revealed a decrease in relative protein abundance that correlated with (decreasing) egg quality in one major group (heat-shock proteins). No differences were found in the other protein groups. Linear regression analysis, performed for each identified protein separately, revealed seven proteins that showed a significant decrease in relative abundance with reduced blastomere symmetry: two correlates that have been named in other studies (vitellogenin, heat-shock protein-70) and a further five new candidate proteins (78 kDa glucose-regulated protein, elongation factor-2, GTP-binding nuclear protein Ran, iduronate 2-sulfatase and 6-phosphogluconate dehydrogenase). Notwithstanding issues associated with multiple statistical testing, we conclude that these proteins, and especially iduronate 2-sulfatase and the generic heat-shock protein group, could serve as biomarkers of egg quality in hapuku.

The effects of 11-ketotestosterone on ovarian physiology of previtellogenic captive hapuku (Polyprion oxygeneios).

The present study investigated, for the first time in a perciform teleost, the effects of in vivo 11-ketotestosterone (11-KT) treatment using slow-release implants on ovarian development and gonadotropin receptor mRNA levels in captive previtellogenic females of hapuku (Polyprion oxygeneios). At the cellular/functional level, ovarian development and ovarian and hepatic total lipid levels were examined. At the molecular level, transcript abundance of ovarian follicle-stimulating hormone receptor (FSH-R) and luteinizing hormone receptor (LH-R) was measured. Additionally, cyclic adenosine monophosphate (cAMP) levels in ovarian fragments from placebo and 11-KT implanted fish incubated with or without human chorionic gonadotropin (hCG) in vitro were compared between groups. There were no significant differences between treatments with regard to oocyte size and lipid contents of liver and ovary. Messenger RNA levels of FSH-R and LH-R were significantly lower in the treated females. Similarly, cAMP levels were significantly lower in the ovarian fragments of the 11-KT implanted females. These results suggest that 11-KT specifically, but possibly androgens in general, may not have an important function in regulating gonadal development of previtellogenic female hapuku; indeed, if anything, 11-KT appeared to have a detrimental effect and its use will not be beneficial in advancing sexual maturity of hapuku in aquaculture.