An overview of harmful algal blooms and eutrophication in Jakarta Bay, Indonesia

Algal blooms have been occurring in Jakarta Bay for twenty years. However, recently the occurrence of algal blooms, their harmful effects, and their duration have been intensified. Algal blooms have devastated the marine environment, caused fish mortality, and been detrimental to local tourism, local fishing, and other industries along the coast. It comes to speculation that the increase of anthropogenic activity from surrounding areas is taking a toll on the environment. So, this research aimed to study the recent rise of algal blooms in Jakarta Bay and the possible anthropogenic links, mainly through cultural eutrophication, to the increasing occurrence of red tides and their impact. Observation has been conducted to study the dynamic of algal blooms concerning eutrophication and the existing seasons. Collecting samples were performed using a canonical plankton net from 2008 until 2015. The results showed that the abundance of phytoplankton ranged from 40.90 x 106 up to 1699.10 x 106 cells.m−3. The highest quantity of cells was observed in May 2010 between rainy to dry seasons. There is evidence that the reported increase in frequency and magnitude of algal bloom events in Jakarta Bay is linked to cultural eutrophication. The recent exponential growth of the city may be a contributing factor in the increasing intensity of algal blooms. The cultural eutrophication of coastal waters increased, leading to the intensity and frequency of algal bloom.

Dealing with the Understanding of the Dynamics Related to Multifactorial Temporal Interactions That Spatially Affect the Landscape of Coastal Lagoons

Models based on multifactorial interactions are needed to deal with the dynamics taking place in the eutrophication processes of coastal lagoons. However, as the number of indirect drivers stemming from anthropogenic factors increases, temporal disorders between anthropogenic activities may increase, thus hindering the understanding of their dynamics. We have built multifactorial pathways to deal with the dynamics associated with the cultural eutrophication process of a coastal lagoon. The pathways guided the identification of potential temporal disorder patterns between anthropogenic activities, which may exert influence on the disturbances associated with eutrophication process. The identification of temporal disorder patterns derived from anthropogenic activities belonging to different pathways resulted in a valuable form of support for analyzing and evaluating relationships between public policies, technological skills and environmental culture programs. All of which exert influence on the eutrophication process, which in turn cause changes on the trophic state and on the landscape of the coastal lagoon. Pathways composed of multifactorial interactions that take into account spatial and temporal aspects, contribute to improving the understanding of the inherent dynamics of the eutrophication process of coastal lagoons. Temporal disorders between anthropogenic activities may be seen to emerge, thus exerting changes on the trophic state and spatial damage on the landscapes of coastal lagoons.

Feasibility Analysis of the Sustainability of the Tres Palos Coastal Lagoon: A Multifactorial Approach

We studied the cultural eutrophication process assessments of coastal lagoons by considering sociopolitical, socioeconomic, demographic, technological, and cultural factors, which represent indirect drivers exerting effects on the eutrophication process, causing changes on the trophic status. Multifactorial interactions in eutrophication processes make understanding their complex dynamics difficult, leading to unreliable assessments and, consequently, to unsustainable management actions. This, in turn, hinders the feasibility of coastal lagoon sustainability. We propose a method based on the evaluation of pathways derived from a multifactorial network, which represents the eutrophication process, with the aim of determining the feasibility of the sustainability of the Tres Palos coastal lagoon. Our findings revealed that most of the evaluations of relationships belonging to pathways were unfeasible due to reasons such as: there was no evidence of the existence of public policies, technological skills, and cultural factors; there was a lack of data related to human settlements around the lagoon and river, industrial waste, agricultural practices, and tourism. The preceding shortcomings hinder the feasibility of coastal lagoon sustainability under study. We suggest that assessments of cultural eutrophication processes that overlook sociopolitical, socioeconomic, technological, and cultural factors are limited and inadequate for supporting the feasibility of sustainable coastal lagoons.

Does Warming Enhance the Effects of Eutrophication in the Seagrass Posidonia oceanica?

Seagrass meadows are disappearing at rates comparable to those reported for mangroves, coral reefs, and tropical rainforests. One of the main causes of their decline is the so-called cultural eutrophication, i.e., the input of abnormal amounts of nutrients derived from human activities. Besides the impact of eutrophication at a local scale, the occurrence of additional stress factors such as global sea warming may create synergisms in detriment of seagrass meadows’ health. In the present study, we aimed to evaluate if plants undergoing chronic cultural eutrophication and plants growing in relatively pristine waters are more (or less) sensitive to heat stress, nutrient load and the combination of both stressors. To address this question, a mesocosm experiment was conducted using Posidonia oceanica collected from two environments with different nutrients load history. Plants were exposed in controlled conditions to high nutrient concentrations, increased temperature and their combination for 5 weeks, to assess the effect of the single stressors and their interaction. Our results revealed that plants experiencing chronic cultural eutrophication (EU) are more sensitive to further exposure to multiple stressors than plants growing in oligotrophic habitats (OL). OL and EU plants showed different morphological traits and physiological performances, which corroborates the role of local pressures in activating different strategies in response to global environmental changes. EU-plants appeared to be weaker during the treatments, showing the greatest percentage of mortality, particularly under increased temperature. Temperature and nutrient treatments showed opposite effects when tested individually and an offset response when combined. The activation of physiological strategies with high energetic expenses to cope with excess of nutrients and other stressors, could affect plants present and future persistence, particularly under eutrophic conditions. Our results represent a step forward in understanding the complex interactions that occur in natural environments. Moreover, unraveling intraspecific strategies and the role of local acclimation/adaptation in response to multiple stressors could be crucial for seagrass conservation strategies under a climate change scenario.