Simulated eutrophication and browning alters zooplankton nutritional quality and determines juvenile fish growth and survival

The first few months of life is the most vulnerable period for fish and their optimal hatching time with zooplankton prey is favored by natural selection. Traditionally, however, prey abundance (i.e., zooplankton density) has been considered important, whereas prey nutritional composition has been largely neglected in natural settings. High-quality zooplankton, rich in both essential amino acids (EAAs) and fatty acids (FAs), are required as starting prey to initiate development and fast juvenile growth. Prey quality is dependent on environmental conditions, and, for example, eutrophication and browning are two major factors defining primary producer community structures that will directly determine the nutritional quality of the basal food sources (algae, bacteria, terrestrial matter) for zooplankton. We experimentally tested how eutrophication and browning affect the growth and survival of juvenile rainbow trout (Oncorhynchus mykiss) by changing the quality of basal resources. We fed the fish on herbivorous zooplankton (Daphnia) grown with foods of different nutritional quality (algae, bacteria, terrestrial matter), and used GC-MS, stable isotope labeling as well as bulk and compound-specific stable isotope analyses for detecting the effects of different diets on the nutritional status of fish. The content of EAAs and omega-3 (ω-3) polyunsaturated FAs (PUFAs) in basal foods and zooplankton decreased in both eutrophication and browning treatments. The decrease in ω-3 PUFA and especially docosahexaenoic acid (DHA) was reflected to fish juveniles, but they were able to compensate for low availability of EAAs in their food. Therefore, the reduced growth and survival of the juvenile fish was linked to the low availability of DHA. Fish showed very low ability to convert alpha-linolenic acid (ALA) to DHA. We conclude that eutrophication and browning decrease the availability of the originally phytoplankton-derived DHA for zooplankton and juvenile fish, suggesting bottom-up regulation of food web quality.Peer reviewe

Mitogenomics of Blasia pusilla as a tool for agricultural productivity

Agricultural productivity is a growing concern and several key genomes have been sequenced with the goal of exploring how traits of genomic adaptation could be transferred to cultivated crops, this having been the cornerstone of crop research. Much of the focus has been on crop species that have been directly used to address human needs, considering projected population growth up until 2050 and beyond. However, it is likely that a deeper understanding of mechanisms that could be used to engineer crops will come from the study of early embryophytes (land plants) and closely related freshwater green algae, traits from which could be exploited to boost crop productivity in terms of genomic adaptation with a view towards understanding the basic building blocks of crop engineering. We present the mitogenome of Blasia pusilla (an early embryophyte), assembled using PACBIO SMRT and Illumina sequencing and highlights its role from the phylogenetic perspective.Peer reviewe