Aquatic Ecology最新文献

Aquatic plants suffer stress caused by abiotic and biotic variables. In estuaries, salinity is one of the main abiotic factors responsible for stress. This study aimed to evaluate oxidative stress in two species of aquatic macrophytes (Crinum americanum and Spartina alterniflora) that are common in Brazilian tropical estuaries. We measured reactive oxygen species (hydrogen peroxide and malondialdehyde) and total nitrogen (TN) and total phosphorus (TP) in the aboveground and belowground biomass of the species. In addition, we measured salinity, TN, and TP content in the sediment. Statistical tests included t test and the analysis of variance (ANOVA) followed by the Tukey’s test. Our results showed that the greatest oxidative stress, in both species, occurred in areas of the estuary with lower salinity. For C. americanum, limitation by TN and TP content in the sediment is the main cause of oxidative stress. For S. alterniflora, the presence of C. americanum and the allelopathic compounds released by it seem to be the major cause of oxidative stress. Salinity did not induce oxidative stress in C. americanum and S. alterniflora in the estuary; however, the difference in TP and TN contents in the sediment played an important role in their responses to oxidative stress.

Leaf traits and chloroplast structure have a direct impact on plant growth rates. Fast-growing species allocate more carbon to growth, and slow-growing species invest more in storage. This study was conducted to investigate the fast-growing mechanism of the introduced mangrove species Laguncularia racemosa, by comparing the leaves of L. racemosa and three slow-growing native mangrove species (Kandelia obovata, Avicennia marina, and Aegiceras corniculatum) through analysis of anisotropic growth of leaf traits and leaf chloroplast ultrastructure. The results showed that the largest slope values were found in the leaf area compared to leaf perimeter relationship (2.035), while the slope of the leaf perimeter compared to leaf width relationship was only 0.832. And the leaf area of A. marina was most influenced by leaf perimeter, while the leaf area of L. racemosa was least influenced by leaf perimeter. Furthermore, the average area of thylakoid lamellae per chloroplast was the largest in L. racemosa leaves, with no accumulation of starch granules detected. While most of the chloroplast area of three native mangrove species was occupied by starch granules and lipid droplets, resulting in a reduction in the thylakoid lamellae contained per unit area of the chloroplasts. These results imply that the chloroplasts of L. racemosa can transport photosynthetic products to other organs of the plant in a timely manner, maximizing the area of thylakoid lamellae in the chloroplast and enabling its leaves to maintain high photosynthesis for its rapid growth.

The Portuguese man-of-war is responsible for the most common and severe stings worldwide. Jellyfish monitoring is essential to manage stings, and social media is a valuable data source for obtaining observations of this species. This study reports on using Convolutional Neural Networks for Portuguese man-of-war image classification extracted from social media posts. We created a suitable dataset and trained three different neural networks: VGG-16, ResNet50, and InceptionV3, with and without a pre-trained step with the ImageNet dataset. The pre-trained ResNet50 network presented the best results, obtaining 94% accuracy and 95% precision, recall, and F1 score. We conclude that Convolutional Neural Networks can be very effective for recognizing Portuguese man-of-war images from social media, helping in obtaining data about its occurrence and distribution.

This study focuses on the analyses of the gastral cavity contents of two species of Ceriantharia, namely Isarachnanthus nocturnus Hartog, 1977, collected in São Sebastião, Brazil, and Pachycerianthus magnus Nakamoto, 1919, collected from two points along the coast of Okinawa Island, Japan. Both morphological (light microscopy) and metagenomic (whole-genome shotgun sequencing) analyses were conducted with the aim of identifying the main classes of organisms that make up the diet of these species. The results revealed that morphological analyses were not sufficient for identifying prey organisms, but metagenomic analyses showed a diverse range of animal classes, indicating the varied diet of these ceriantharians. The most abundant classes observed in the contents of both species were Anthozoa, Aconoidasida, Kinetoplastea, Actinopterygii, Insecta, and Leptocardii. This finding suggests a cohesive feeding pattern among these two species from distant areas, providing a more comprehensive understanding of their feeding performance and contributing to studies on the subclass Ceriantharia.

Calanoid copepods have gained significant interest due to their rapid response to changes in environment. This study examined the seasonal variation in the size of calanoid copepods and their relationships to various environmental parameters in a tropical coast of India. Zooplankton samples were collected at Marina Beach, India, from January to December 2021. Ten calanoid species were selected based on their distribution to study the seasonal variation in the size, and the results showed a clear seasonal pattern, with smaller size of calanoid observed during summer months with high temperatures and larger sizes during the monsoon season associated with increased rainfall and nutrient availability. Negative correlations were observed between copepod size variation and temperature, while positive correlations were observed with dissolved oxygen, pH, salinity, and chlorophyll-a concentration. Acrocalanus gibber, Acrocalanus gracilis and Canthocalanus pauper showed changes that are more pronounced in body size (0.89–0.99, 1.12–1.23 mm and 1.41–1.52 mm, respectively) indicating species-specific responses to environmental fluctuations. These findings highlight the influence of environmental parameters in determining the size of calanoid copepods in tropical oceans. Moreover, this study contributes to our understanding of the ecological processes and global warming that determine copepod size variation in coastal ecosystems.

Despite jellyfish’s ecological and socioeconomic impacts, they are still an understudied component of marine ecosystems. Even with its conspicuous size, reaching ~ 1 m in bell diameter, Drymonema gorgo has been rarely observed, with only a few occurrences in the literature, suggesting that it is not a common species. Here, we gathered historical records from literature, personal communication, and novel data from the World Wide Web (WWW) to obtain observations of D. gorgo along the Brazilian coast. A total of 63 observations from 1857 to 2022 were compiled, of which 57 were extracted from the web. Observations on this jellyfish concentrated between 22° S and 27° S, especially in the Cabo Frio region in Rio de Janeiro. They were reported throughout the year, except in August and October, with the highest concentrations in March (late summer). Based on the notable complement on information about its occurrence in the last ten years, we hypothesize that D. gorgo is probably not as rare as suggested by the near absence of previous literature records. In addition, biological associations of D. gorgo with other species were also discovered such as (1) predation on the jellyfish Aurelia sp. and Chrysaora lactea; (2) food item for the green turtle Chelonia mydas; and (3) association with fishes. This study provides evidence of the potential use of the WWW to obtain ecological data about conspicuous marine species occurrence, such as D. gorgo, helping to fill knowledge gaps and overcome difficulties in its detection using traditional methodologies.

An analysis of ectoparasite infestations in Champsocephalus gunnari at South Orkney Islands, Antarctica, was performed, which revealed the prevalence, mean abundance, and mean intensity of the two species of parasites collected. The parasites’ preference for parts of the infested host fish was also investigated. The host–parasite trophic relationship was further examined using stable carbon and nitrogen isotopic analysis. The results showed that Eubrachiella antarctica was more inclined to parasitize the fins of C. gunnari. The carbon isotope ratio (δ¹³C) of the host was negatively correlated with the values for carbon isotopic discrimination (Δδ¹³C) between host and E. antarctica. The relationship between E. antarctica and C. gunnar is considered “parasitic” because E. antarctica has a higher trophic level than that of host C. gunnari, while Trulliobdella capitis may be a carrier parasite of C. gunnari or show a “symbiotic” relationship with it. The ecological niche spaces of the three species do not overlap, indicating the existence of specific trophic niches in the marine food web.

Cyanobacterial harmful algal blooms (cyanoHABs) are extremely detrimental to the environment and cause sizable economic losses. Microcystis aeruginosa is reported to be inhibited by Eurasian watermilfoil (Myriophyllum spicatum), and onset of the inhibitory effects of M. spicatum varied depending on the seasons. This study aimed to investigate the seasonal allelopathy effects in the metabolomes of M. spicatum using gas chromatography–mass spectrometry and predict the most effective season for its allelopathic inhibitory effects on the growth of M. aeruginosa. A machine learning approach using multi-layer perceptron was used to predict the season with maximum anti-cyanobacterial potential. The prediction model suggested that M. spicatum collected in August would have higher growth-inhibiting effects than other months with 93.6 (± 2.9) likelihood. These results were consistent with coexistence experiments where M. spicatum collected in August showed the earliest onset of inhibition. The study concluded that the inhibitory potential of M. spicatum on cyanobacterial growth was strong in the summer, especially in August. This suggests that neural network machine learning can be applied to a variety of topics using accumulated data, making clearer and more useful predictions possible even in multivariate and complex environmental data.

Gelatinous zooplankton are essential components of healthy ecosystems. Given their characteristic life cycle, ecological aspects and adaptability to a variety of oceanic conditions, these organisms are considered indicators of climate change, having particular advantages relative to other taxa. Citizen science initiatives are becoming increasingly frequent, providing data that are otherwise difficult to collect and interesting results for different taxa worldwide, allowing for example the detection of new occurrences. The ongoing citizen science program GelAvista, running since 2016, gathers data reported by observers on jellyfish occurrences in Portuguese waters, in the north-eastern Atlantic. The program has enhanced the knowledge of these organisms, providing data on biodiversity, and the dynamics of their distribution and abundance. Particular sightings of hydromedusae were received through GelAvista for mainland Portugal, close to the Tagus River, in the Lisbon Bay region. The species was morphologically and molecularly identified as Odessia maeotica, comprising its first reported occurrence in the Lisbon Bay. The details on the occurrence of the species are provided and discussed given the current knowledge of the species.