scholarly journals Reversal of a cyanobacterial bloom in response to early warnings

2016 ◽  
Vol 114 (2) ◽  
pp. 352-357 ◽  
Author(s):  
Michael L. Pace ◽  
Ryan D. Batt ◽  
Cal D. Buelo ◽  
Stephen R. Carpenter ◽  
Jonathan J. Cole ◽  
...  

Directional change in environmental drivers sometimes triggers regime shifts in ecosystems. Theory and experiments suggest that regime shifts can be detected in advance, and perhaps averted, by monitoring resilience indicators such as variance and autocorrelation of key ecosystem variables. However, it is uncertain whether management action prompted by a change in resilience indicators can prevent an impending regime shift. We caused a cyanobacterial bloom by gradually enriching an experimental lake while monitoring an unenriched reference lake and a continuously enriched reference lake. When resilience indicators exceeded preset boundaries, nutrient enrichment was stopped in the experimental lake. Concentrations of algal pigments, dissolved oxygen saturation, and pH rapidly declined following cessation of nutrient enrichment and became similar to the unenriched lake, whereas a large bloom occurred in the continuously enriched lake. This outcome suggests that resilience indicators may be useful in management to prevent unwanted regime shifts, at least in some situations. Nonetheless, a safer approach to ecosystem management would build and maintain the resilience of desirable ecosystem conditions, for example, by preventing excessive nutrient input to lakes and reservoirs.

2018 ◽  
Vol 10 (2) ◽  
pp. 286-314 ◽  
Author(s):  
Matthew Osborne

This paper estimates a cost-of-living index using a dynamic structural model for two storable product categories. In each category, regime shifts to higher or lower retail prices are observed. Fixed-base indexes do a poor job of capturing changes in welfare after a regime shift, and deviate from the dynamic index by as much as 300 percent. I evaluate the extent to which two recently proposed indexes can approximate the model-derived index. These indexes improve welfare measurement and are straightforward to compute. The category’s competitive structure and features of the regime shift determine which of the two provides a better approximation. (JEL C43, C51, E31, L11)


2020 ◽  
Vol 12 (9) ◽  
pp. 3704
Author(s):  
Lei Zhao ◽  
Mingguo Wang ◽  
Zhongyao Liang ◽  
Qichao Zhou

Regime shifts in shallow lakes can lead to great changes in ecosystem structures and functions, making ecosystem management more complicated. Lake Yilong, located in Yunnan Province, is one of the most eutrophic lakes in China. Although there is a high possibility that this lake has undergone regime shift one or more times, the presence of regime shifts and their drivers remain unknown. Here, we employed the sequential t-test analysis of regime shifts to detect the regime shifts based on the long-term (1989–2018) dataset of the lake. We further determined their potential drivers, and explored the nutrient thresholds of regime shifts and hysteresis. The results showed that during the testing period, three regime shifts occurred in 1996 (restorative type), 2009 (catastrophic type) and 2014 (restorative type). The potential key drivers for the first two regime shifts (1996 and 2009) were both related to aquaculture. The abolition of cage fish culture may have led to the restorative regime shift in 1996, and the stocking of crabs and excessive premature releasing of fry possibly caused the catastrophic regime shift in 2009. However, the third regime shift, which occurred in 2014, was possibly related to the drought and succedent hydration. These results indicate that adjustments of aquaculture strategy and hydrological conditions are critical for the lake ecosystem’s recovery. Moreover, the total phosphorus thresholds were identified to be lower than 0.046 mg/L (restorative type) and higher than 0.105 mg/L (catastrophic type), respectively. In addition, an obvious hysteresis was observed after 2014, suggesting that nutrient reduction is important for this lake’s management in the future.


Science ◽  
2018 ◽  
Vol 362 (6421) ◽  
pp. 1379-1383 ◽  
Author(s):  
Juan C. Rocha ◽  
Garry Peterson ◽  
Örjan Bodin ◽  
Simon Levin

Regime shifts are large, abrupt, and persistent critical transitions in the function and structure of ecosystems. Yet, it is unknown how these transitions will interact, whether the occurrence of one will increase the likelihood of another or simply correlate at distant places. We explored two types of cascading effects: Domino effects create one-way dependencies, whereas hidden feedbacks produce two-way interactions. We compare them with the control case of driver sharing, which can induce correlations. Using 30 regime shifts described as networks, we show that 45% of regime shift pairwise combinations present at least one plausible structural interdependence. The likelihood of cascading effects depends on cross-scale interactions but differs for each type. Management of regime shifts should account for potential connections.


2016 ◽  
Vol 113 (33) ◽  
pp. 9315-9320 ◽  
Author(s):  
Giovanni Sandrini ◽  
Xing Ji ◽  
Jolanda M. H. Verspagen ◽  
Robert P. Tann ◽  
Pieter C. Slot ◽  
...  

Rising atmospheric CO2 concentrations are likely to affect many ecosystems worldwide. However, to what extent elevated CO2 will induce evolutionary changes in photosynthetic organisms is still a major open question. Here, we show rapid microevolutionary adaptation of a harmful cyanobacterium to changes in inorganic carbon (Ci) availability. We studied the cyanobacterium Microcystis, a notorious genus that can develop toxic cyanobacterial blooms in many eutrophic lakes and reservoirs worldwide. Microcystis displays genetic variation in the Ci uptake systems BicA and SbtA, where BicA has a low affinity for bicarbonate but high flux rate, and SbtA has a high affinity but low flux rate. Our laboratory competition experiments show that bicA + sbtA genotypes were favored by natural selection at low CO2 levels, but were partially replaced by the bicA genotype at elevated CO2. Similarly, in a eutrophic lake, bicA + sbtA strains were dominant when Ci concentrations were depleted during a dense cyanobacterial bloom, but were replaced by strains with only the high-flux bicA gene when Ci concentrations increased later in the season. Hence, our results provide both laboratory and field evidence that increasing carbon concentrations induce rapid adaptive changes in the genotype composition of harmful cyanobacterial blooms.


2015 ◽  
Vol 370 (1659) ◽  
pp. 20130263 ◽  
Author(s):  
Vasilis Dakos ◽  
Stephen R. Carpenter ◽  
Egbert H. van Nes ◽  
Marten Scheffer

In the vicinity of tipping points—or more precisely bifurcation points—ecosystems recover slowly from small perturbations. Such slowness may be interpreted as a sign of low resilience in the sense that the ecosystem could easily be tipped through a critical transition into a contrasting state. Indicators of this phenomenon of ‘critical slowing down (CSD)’ include a rise in temporal correlation and variance. Such indicators of CSD can provide an early warning signal of a nearby tipping point. Or, they may offer a possibility to rank reefs, lakes or other ecosystems according to their resilience. The fact that CSD may happen across a wide range of complex ecosystems close to tipping points implies a powerful generality. However, indicators of CSD are not manifested in all cases where regime shifts occur. This is because not all regime shifts are associated with tipping points. Here, we review the exploding literature about this issue to provide guidance on what to expect and what not to expect when it comes to the CSD-based early warning signals for critical transitions.


2016 ◽  
Vol 283 (1825) ◽  
pp. 20152569 ◽  
Author(s):  
Johanna Yletyinen ◽  
Örjan Bodin ◽  
Benjamin Weigel ◽  
Marie C. Nordström ◽  
Erik Bonsdorff ◽  
...  

Species composition and habitats are changing at unprecedented rates in the world's oceans, potentially causing entire food webs to shift to structurally and functionally different regimes. Despite the severity of these regime shifts, elucidating the precise nature of their underlying processes has remained difficult. We address this challenge with a new analytic approach to detect and assess the relative strength of different driving processes in food webs. Our study draws on complexity theory, and integrates the network-centric exponential random graph modelling (ERGM) framework developed within the social sciences with community ecology. In contrast to previous research, this approach makes clear assumptions of direction of causality and accommodates a dynamic perspective on the emergence of food webs. We apply our approach to analysing food webs of the Baltic Sea before and after a previously reported regime shift. Our results show that the dominant food web processes have remained largely the same, although we detect changes in their magnitudes. The results indicate that the reported regime shift may not be a system-wide shift, but instead involve a limited number of species. Our study emphasizes the importance of community-wide analysis on marine regime shifts and introduces a novel approach to examine food webs.


2005 ◽  
Vol 62 (3) ◽  
pp. 328-332 ◽  
Author(s):  
Sergei Rodionov ◽  
James E. Overland

Abstract A common problem of existing methods for regime shift detection is their poor performance at the ends of time-series. Consequently, shifts in environmental and biological indices are usually detected long after their actual appearance. A recently introduced method based on sequential t-test analysis of regime shifts (STARS) treats all incoming data in real time, signals the possibility of a regime shift as soon as possible, then monitors how perception of the magnitude of the shift changes over time. Results of a STARS application to the eastern Bering Sea ecosystem show how the 1989 and 1998 regime shifts manifest themselves in biotic and abiotic indices in comparison with the 1977 shift.


2010 ◽  
Vol 3 (1) ◽  
pp. 103-119
Author(s):  
Michał Marosz

Abstract Arctic Oscillation (AO) reflects the dominating mode of SLP (or 1000hPa) variability in hemispheric scale and seems to bear an effect on the weather and, in longer time scales, on climate. The aim of the research was to identify the possible regime shifts in the multiannual course of AO index which in turn might be utilised in the identification and quantification of the regional/local meteorological field response. The data (AO monthly and daily index values) were acquired from the NOAA Climate Prediction Centre. The AO index is constructed by projecting monthly/daily anomalies of 1000hPa heights poleward of 20°N onto the loading pattern of the AO - 1st (leading) EOF of the 1000hPa height field for the same spatial domain. The temporal scope of analysis was 1951-2009. The analysis comprised the regime shift identification techniques that track the shifts in the mean values and in the magnitude of fluctuations as well as the usage of the classical linear trend identification in the annual and seasonal scale. The regime shift recognition was followed by the compositing method that allowed the analysis of spatial anomalies in SLP field in Euro-Atlantic region that reflect the response of the regional airflow to identified circulation regimes.


2021 ◽  
Vol 9 (8) ◽  
pp. 1711
Author(s):  
Marie-Charlotte Cheutin ◽  
Sébastien Villéger ◽  
Christina C. Hicks ◽  
James P. W. Robinson ◽  
Nicholas A. J. Graham ◽  
...  

Replacement of coral by macroalgae in post-disturbance reefs, also called a “coral-macroalgal regime shift”, is increasing in response to climate-driven ocean warming. Such ecosystem change is known to impact planktonic and benthic reef microbial communities but few studies have examined the effect on animal microbiota. In order to understand the consequence of coral-macroalgal shifts on the coral reef fish enteric bacteriome, we used a metabarcoding approach to examine the gut bacteriomes of 99 individual fish representing 36 species collected on reefs of the Inner Seychelles islands that, following bleaching, had either recovered to coral domination, or shifted to macroalgae. While the coral-macroalgal shift did not influence the diversity, richness or variability of fish gut bacteriomes, we observed a significant effect on the composition (R2 = 0.02; p = 0.001), especially in herbivorous fishes (R2 = 0.07; p = 0.001). This change is accompanied by a significant increase in the proportion of fermentative bacteria (Rikenella, Akkermensia, Desulfovibrio, Brachyspira) and associated metabolisms (carbohydrates metabolism, DNA replication, and nitrogen metabolism) in relation to the strong turnover of Scarinae and Siganidae fishes. Predominance of fermentative metabolisms in fish found on macroalgal dominated reefs indicates that regime shifts not only affect the taxonomic composition of fish bacteriomes, but also have the potential to affect ecosystem functioning through microbial functions.


2019 ◽  
Vol 11 (4) ◽  
pp. 1139 ◽  
Author(s):  
Jose De Alban ◽  
Graham Prescott ◽  
Kevin Woods ◽  
Johanness Jamaludin ◽  
Kyaw Latt ◽  
...  

Regime shifts—rapid long-term transitions between stable states—are well documented in ecology but remain controversial and understudied in land use and land cover change (LUCC). In particular, uncertainty surrounds the prevalence and causes of regime shifts at the landscape level. We studied LUCC dynamics in the Tanintharyi Region (Myanmar), which contains one of the last remaining significant contiguous forest areas in Southeast Asia but was heavily deforested between 1992–2015. By combining remote sensing methods and a literature review of historical processes leading to LUCC, we identified a regime shift from a forest-oriented state to an agricultural-oriented state between 1997–2004. The regime shift was triggered by a confluence of complex political and economic conditions within Myanmar, notably the ceasefires between various ethnic groups and the military government, coupled with its enhanced business relations with Thailand and China. Government policies and foreign direct investment enabling the establishment of large-scale agro-industrial concessions reinforced the new agriculture-oriented regime and prevented reversion to the original forest-dominated regime. Our approach of integrating complementary analytical frameworks to identify and understand land-cover regime shifts can help policymakers to preempt future regime shifts in Tanintharyi, and can be applied to the study of land change in other regions.


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