RESUMO

Species diversity underpins all ecosystem services that support life. Despite this recognition and the great advances in detecting biodiversity, exactly how many and which species co-occur and interact, directly or indirectly in any ecosystem is unknown. Biodiversity accounts are incomplete; taxonomically, size, habitat, mobility or rarity biased. In the ocean, the provisioning of fish, invertebrates and algae is a fundamental ecosystem service. This extracted biomass depends on a myriad of microscopic and macroscopic organisms that make up the fabric of nature and which are affected by management actions. Monitoring them all and attributing changes to management policies is daunting. Here we propose that dynamic quantitative models of species interactions can be used to link management policy and compliance with complex ecological networks. This allows managers to qualitatively identify 'interaction-indicator' species, which are highly impacted by management policies through propagation of complex ecological interactions. We ground the approach in intertidal kelp harvesting in Chile and fishers' compliance with policies. Results allow us to identify sets of species that respond to management policy and/or compliance, but which are often not included in standardized monitoring. The proposed approach aids in the design of biodiversity programmes that attempt to connect management with biodiversity change. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'.

Assuntos

RESUMO

Top-down and bottom-up forces determine ecosystem function and dynamics. Fisheries as a top-down force can shorten and destabilize food webs, while effects driven by climate change can alter the bottom-up forces of primary productivity. We assessed the response of a highly-resolved intertidal food web to these two global change drivers, using network analysis and bioenergetic modelling. We quantified the relative importance of artisanal fisheries as another predator species, and evaluated the independent and combined effects of fisheries and changes in plankton productivity on food web dynamics. The food web was robust to the loss of all harvested species but sensitive to the decline in plankton productivity. Interestingly, fisheries dampened the negative impacts of decreasing plankton productivity on non-harvested species by reducing the predation pressure of harvested consumers on non-harvested resources, and reducing the interspecific competition between harvested and non-harvested basal species. In contrast, the decline in plankton productivity increased the sensitivity of harvested species to fishing by reducing the total productivity of the food web. Our results show that strategies for new scenarios caused by climate change are needed to protect marine ecosystems and the wellbeing of local communities dependent on their resources.

RESUMO

Salmon farming is a widespread activity around the world, also known to promote diverse environmental effects on aquatic ecosystems. However, information regarding the impact of salmon farming on bird assemblages is notably scarce. We hypothesize that salmon farming, by providing food subsidies and physical structures to birds, will change their local community structure. To test this hypothesis, we conducted a seasonal monitoring of bird richness, abundance, and composition at paired salmon pen and control plots in two marine and two lake sites in southern Chile, from fall 2002 to summer 2004. Overall, salmon farming had no significant effects on species richness, but bird abundance was significantly and noticeably higher in salmon pens than in controls. Such aggregation was mainly accounted for by the trophic guilds of omnivores, diving piscivores, carrion eaters, and perching piscivores, but not by invertebrate feeders, herbivores, and surface feeders. Species composition was also significantly and persistently different between salmon pens and controls within each lake or marine locality. The patterns described above remained consistent across environment types and seasons indicating that salmon farming is changing the community structure of birds in both lake and marine habitats by promoting functional and aggregation responses, particularly by favoring species with broader niches. Such local patterns may thus anticipate potential threats from the ongoing expansion of the salmon industry to neighboring areas in Chile, resulting in regional changes of bird communities, toward a less diverse one and dominated by opportunistic, common, and generalist species such as gulls, vultures, and cormorants.

Assuntos

RESUMO

Pregnancy per artificial insemination (AI) was evaluated in dairy cows (Bos taurus) subjected to synchronization and resynchronization for timed AI (TAI). Cows (n=718) received prostaglandin F(2alpha) (PGF) on Days -38 and -24 (Days 39 and 53 postpartum), gonadotropin-releasing hormone (GnRH) on Day -10, PGF on Day -3, and GnRH and TAI on Day 0. Between Days -10 and -3, cows received a progesterone intravaginal insert (CIDR group) or no CIDR (Control group). Between Days 14 and 23, cows received a CIDR (Resynch CIDR group) or no CIDR (Resynch control group), GnRH on Day 23, with pregnancy diagnosis on Day 30. Cows in estrus (between Days 0 and 30) were re-inseminated at detected estrus (RIDE). Nonpregnant cows received PGF on Day 30 and GnRH and TAI on Day 33. Plasma progesterone was determined to be low or high on Days -24 and -10. Pregnancy rates were evaluated 30 and 55 d after AI. The CIDR insert included in the Presynch-Ovsynch protocol did not increase overall pregnancy per AI for first service (36.1% and 33.6% for CIDR; 34.1% and 28.8% for Control) but did decrease pregnancy loss (7.0% for CIDR and 15.6% for Control). The CIDR insert increased pregnancy per AI in cows with high progesterone at the time the CIDR insert was applied. Administration of a CIDR insert between Days 14 and 23 of the estrous cycle after first service did not increase overall pregnancy per AI to second service (24.7% and 22.7% for Resynch CIDR; 28.6% and 25.3% for Resynch control). For second service, RIDE cows had lower pregnancy rates in the Resynch CIDR group than in the Resynch control group. Cows with a CL (corpus luteum) at Day 30 had higher pregnancy rates in the Resynch CIDR group than those in the Resynch control group.

Assuntos