Oceans absorb a huge part of the atmospheric heat, leading to the rise in water temperature. Reefs are among the most affected ecosystems, where the complex behavioral repertoire of fishes is usually ...an indicator of environmental impacts. Here, we examined whether temperature (28 and 34°C) and habitat complexity (high and low) interact to affect the agonistic behavior (mirror test) of the dusky damselfish (Stegastes fuscus), a key species in Brazilian reefs because of its gardening capacity and territorial behavior. Higher temperatures altered basal behavior in both high and low-complexity conditions. Fish kept at 28°C under the high-complexity condition were more aggressive than those at a higher temperature (34°C) and in a low-complexity condition, which also exhibited lower dispersion. Our data show that changes in behavior of coral reef fish is associated to fluctuations in environmental conditions. Thus, it is important to implement management or conservation strategies that could mitigate global change effects.
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•Volunteer divers recorded data for all species selected for the monitoring protocol.•Diving experience did not affect data collection.•Volunteer divers estimated abundance and size ...similarly to trained scientific divers.•Volunteer divers recorded flagship species, complementing traditional surveys.•Recreational divers enjoyed the citizen-science experience, attesting its potential.
Overfishing, pollution and global changes threaten reef ecosystems all over the world and several conservation actions emerged to reduce and mitigate such impacts. Citizen-based programs with hands-on conservation experience and voluntarily data collection are a successful way of involving society in the conservation process. We developed and tested a citizen-based monitoring protocol to monitor reef fish and sea turtles during regular recreational diving operations, with minimum impact on the routine of the diving company. We compared data collected by volunteer divers and by trained scientists using this protocol, and assessed the influence of the volunteers´ diving experience in data collection. We found that recreational divers were able to record all the species included in the monitoring slate, providing estimates of species abundance and composition that did not differ from those obtained by trained scientific divers using the same protocol. This method also recorded large reef species, such as rays, sharks and turtles more effectively in comparison to traditional scientific surveys conducted in the same area. Such difference indicates complementarity between the citizen-based monitoring protocol and traditional scientific monitoring methods. The diving experience of recreational divers did not affect their ability to characterize reef assemblages and most volunteers provided a positive feedback of their experience as citizen-scientists. Therefore, recreational divers can be powerful citizen-scientists and implementing similar monitoring protocols in reef areas, particularly in marine protected areas where diving activities are allowed and regulated, seems feasible and a good way to engage divers in data collection and marine conservation.
Reefs are highly diverse ecosystems threatened by anthropogenic actions that change their structure and dynamics. Many of these changes have been witnessed by different reef users who hold specific ...knowledge about the reefscape according to their experiences and uses. We aimed to understand whether fishers, divers, and reef scientists have different perceptions of general changes that have occurred in reefs and whether their knowledge converge, diverge or are complementary. We conducted 172 semi-structured interviews with stakeholders from Northeast and Southeast Brazil where either coral or rocky reefs occur, comprising most reefs occurring in the Southwestern Atlantic Ocean. Reef scientists and divers perceived corals have undergone the sharpest declines among reef species and indicate pollution and tourism as the major negative impacts on reefs. On the contrary, fishers noticed greater declines in fishing targets (i.e., groupers) and have hardly noticed differences in coral abundance or diversity over time. Divers had a broader view of changes in reef organisms, with some level of convergence with both reef scientists and fishers, while reef scientists and fishers provided information on more specific groups and economically relevant resources, respectively. The different stakeholders generally agree that reefscapes have undergone negative changes including diversity loss and abundance declines of reef organisms. The complementarity of information among different stakeholders enables a better understanding of how human behavior impact and perceive changes in natural ecosystems, which could be essential to manage reef environments, particularly those without baseline data.
Despite recent findings on the ecological relevance of within population diet variation far less attention has been devoted to the role diet variation for ecological services. Seed dispersal is a key ...ecological service, affecting plant fitness and regeneration based on foraging by fruit-eating vertebrates. Here we used a network approach, widely used to understand how seed-dispersal is organized at the species level, to gain insights into the patterns that emerge at the individual-level. We studied the individual fruit consumption behavior of a South American didelphid Didelphis albiventris, during the cooldry and warm-wet seasons. In species-species networks the heterogeneity in specialization levels generates patterns such as nestedness and asymmetry. Because generalist populations may be comprised of specialized individuals, we hypothesized that network structural properties, such as nestedness, should also emerge at the individual level. We detected variation in fruit consumption that was not related to resource availability, ontogenetic or sexual factors or sampling biases. Such variation resulted in the structural patterns often found in species-species seed-dispersal networks: low connectance, a high degree of nestedness and the absence of modules. Moreover structure varied between the warm-wet and cool-dry seasons, presumably as a consequence of seasonal fluctuation in fruit availability. Our findings suggest individuals may differ in selectivity causing asymmetries in seed dispersal efficiency within the population. In this sense the realized dispersal would differ from the expected dispersal estimated from their average dispersal potential. Additionally the results suggest possible frequency-dependent effects on seed dispersal that might affect individual plant performance and plant community composition.
Space can be limited in reef ecosystems leading to competitive interactions among sessile organisms. Some competitive mechanisms can require physical contact while others operate with proximity ...between organisms. We investigated how the scleractinian coral
Siderastrea stellata
and the hydrocoral
Millepora alcicornis
respond to physical contact and proximity to the macroalga
Dictyopteris delicatula
and the zoanthid
Palythoa caribaeorum
, common pairs of interactions in Southwestern Atlantic reefs in Northeast Brazil. We held two colonies of the same species within the same tank, one in physical contact and the other within 5 cm of the competitor for four days with macroalgae and three days with the zoanthid. We monitored the corals for 26 days taking photographs and measuring their photosynthetic efficiency (PE) at the point of contact and on the side where competitors were in proximity. Corals were only affected when physically contacted by the competitors, with the macroalga causing a slight damage on
M. alcicornis
and almost no effect on
S. stellata
. Contacts with
P. caribaeorum
reduced the PE and caused tissue discoloration in both corals.
M. alcicornis
recovered after 26 days but the contacted areas of
S
.
stellata
remained discolored and with low PE. Macroalgae and zoanthids required physical contact to damage corals, with the zoanthid causing more damage than the macroalgae. These results suggest that if local and global stressors make corals weaker competitors (e.g. warming) or favor macroalgae and zoanthid growth (e.g. nutrients), corals could be replaced by either of these organisms affecting ecosystem structure and functioning.
Abiotic and biotic stressors are known to trigger reproductive activities in several aquatic organisms. In reef environments, physical contact as a response to competition for space on the benthos is ...a common stressor among sessile organisms, often leading to severe tissue damage and even mortality due to biological and chemical mechanisms. However, the effect of physical stress on coral reproduction has received less attention. In this study, we observed colonies of the scleractinian coral
Siderastrea stellata
releasing larvae in response to physical contact with the zoantharian
Palythoa caribaeorum
. Organisms were collected from reefs in Brazil and taken to the laboratory, where competition through physical contact was simulated in tanks by placing the two species in direct contact for 72 h. During this period, seven out of eight corals that were in physical contact with the zoantharian released larvae, showing tissue discoloration and a marked decrease in photosynthetic efficiency. Only one of the other eight colonies held as a control with no physical contact released larvae, indicating that physical contact may have been the trigger for larval release. This is, to our knowledge, the first report of physical contact-induced larval release in a scleractinian species, providing grounds for further investigating the potential mechanisms involved in this phenomenon.
Here we provide information on the diet of juvenile green turtles from neritic developmental habitats in the South Atlantic that indicates the existence of a gradual dietary shift from a primarily ...carnivorous to a primarily herbivorous diet. Linear regression showed a relation between the size of turtles (n = 22) and the proportion of vegetal matter in the diet, with smaller animals being predominantly carnivorous. We propose 3 hypotheses that could explain these observations.
Abstract Aim Predicting and acting on the future of ecosystems requires understanding species distribution shifts due to climate change. We investigated which corals are more likely to shift their ...distribution in the Southwestern Atlantic under a warming scenario. Location Southwestern Atlantic (SWA; 1° N–28° S). Methods We used spatial distribution models with a Bayesian approach to predict the current and future (2050 and 2100) coral occurrence probabilities of 12 zooxanthellate corals and hydrocorals under an intermediate scenario of increasing greenhouse gas emissions (RCP6.0) projected by the Intergovernmental Panel on Climate Change (IPCC). Results We found a decline in the occurrence probabilities of all 12 taxa within the tropics (1° N–20° S) and an increase towards subtropical sites (20–28° S) as early as 2050. The most significant declines are projected to occur between 9° S and 20° S, a region that currently hosts the richest reef complex in the South Atlantic, the Abrolhos bank. The imminent loss of suitable habitat in the tropics mostly threatens the Brazilian endemics and range restricted corals Mussismilia braziliensis and Mussismilia harttii , while more widely distributed taxa such as Siderastrea spp., Millepora spp. and Porites spp. are expected to expand their ranges southwards. Main Conclusions The projected declines in the tropical region are likely to reduce structural complexity causing biodiversity loss. The overall increase in occurrence probabilities in subtropical areas indicates tropicalisation of SWA reefs, which may benefit species already established in these areas and potentially enrich coral assemblages through the range expansion of taxa that currently do not occur in the region. These findings emphasise the need to support ecological corridors that could aid coral migration towards more suitable habitats under climate change.
Although coral–algae competition is more widely and frequently studied, invertebrates are also major coral competitors, potentially influencing reef structural complexity. Ocean warming can affect ...the outcome of coral–algae interactions, but its effect on the competition between corals and other invertebrates is poorly understood. In Southwestern Atlantic reefs, the branching hydrocoral
Millepora alcicornis
provides important structural complexity but is commonly in contact with the zoanthid
Palythoa caribaeorum
. Considering that
P. caribaeorum
is an efficient competitor that is likely to be more resistant to future ocean warming, the potential replacement of
M. alcicornis
by this zoanthid could reduce reef structural complexity and diversity. We combined field and laboratory experiments to investigate the mechanisms of this hydrocoral–zoanthid interaction, including the role of allelochemicals, to understand the response of
M. alcicornis
to contact by
P. caribaeorum
, and the impact of increasing temperatures on this interaction. Contact with
P. caribaeorum
caused more damage to
M. alcicornis
than the physical control under current temperature (27 °C), both in field and laboratory experiments, but the damaged area recovered within 10 days. Under simulated warming (30 °C) filamentous algae colonized the damaged area, impairing the recovery of
M. alcicornis
. Contact with
P. caribaeorum
chemical extract under current temperature caused more damage to
M. alcicornis
than its control but caused similar damage under warming conditions. These results highlight that warming increased
M. alcicornis
susceptibility to any physical contact and reduced its recovery potential, indicating that it may be outcompeted and overgrown by
P. caribaeorum
as the ocean warms.
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