Blooms Like It Hot

Article · May 2008with4,353 Reads
DOI: 10.1126/science.1155398 · Source: PubMed
A link exists between global warming and the worldwide proliferation of harmful cyanobacterial blooms.
RNA pieces in the spliceosome, has a domain
V counterpart, containing a 2-nucleotide
bulge located 5 base pairs away from an AGC
triad (10). Formation of an analogous metal-
binding platform in this region of U6 (11) may
explain the apparent ability of spliceosomal
RNAs to retain catalytic activity in the com-
plete absence of the many protein components
that usually accompany splicing (12). A
domain V-like element could have played a
major role during the RNA world era of evolu-
tion, serving as the catalytic center for RNA
cleavage, transesterification, and polymeriza-
tion reactions.
The new structure provides a powerful
starting point for future investigations of
group II introns and the spliceosome. The
lack of electron density for domain VI,
which is important for the first step of splic-
ing in many group II introns, and the
absence of exons from the structure preclude
us from seeing how these elements dock
onto the surface created by domains I to V.
Thus, the structural details of substrate
recognition and catalysis remain undefined.
The nature of the conformational change
known to separate the two steps of splicing
(13) also remains unclear. Finally, it will be
important for our understanding of group II
intron self-splicing to capture the structures
of the other intermediates along the splicing
pathway and to pursue experiments that link
features of these structures with functionally
defined interactions.
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of Chemistry, Cambridge, UK, ed. 2, 2008).
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10.1126/science.1156721 SCIENCE VOL 320 4 APRIL 2008
utrient overenrichment of waters by
urban, agricultural, and industrial
development has promoted the
growth of cyanobacteria as harmful algal
blooms (see the figure) (1, 2). These blooms
increase the turbidity of aquatic ecosystems,
smothering aquatic plants and thereby sup-
pressing important invertebrate and fish habi-
tats. Die-off of blooms may deplete oxygen,
killing fish. Some cyanobacteria produce tox-
ins, which can cause serious and occasionally
fatal human liver, digestive, neurological, and
skin diseases (14). Cyanobacterial blooms
thus threaten many aquatic ecosystems,
including Lake Victoria in Africa, Lake Erie in
North America, Lake Taihu in China, and the
Baltic Sea in Europe (36). Climate change is
a potent catalyst for the further expansion of
these blooms.
Rising temperatures favor cyanobacteria
in several ways. Cyanobacteria generally
grow better at higher temperatures (often
above 25°C) than do other phytoplankton
species such as diatoms and green algae (7, 8).
This gives cyanobacteria a competitive advan-
tage at elevated temperatures (8, 9). Warming
of surface waters also strengthens the vertical
stratification of lakes, reducing vertical mix-
ing. Furthermore, global warming causes
lakes to stratify earlier in spring and destratify
later in autumn, which lengthens optimal
growth periods. Many cyanobacteria exploit
these stratified conditions by forming intra-
cellular gas vesicles, which make the cells
buoyant. Buoyant cyanobacteria float upward
when mixing is weak and accumulate in dense
surface blooms (1, 2, 7) (see the figure). These
surface blooms shade underlying nonbuoyant
phytoplankton, thus suppressing their oppo-
nents through competition for light (8).
Cyanobacterial blooms may even locally
increase water temperatures through the
intense absorption of light. The temperatures
of surface blooms in the Baltic Sea and in
Lake IJsselmeer, Netherlands, can be at least
1.5°C above those of ambient waters (10, 11).
This positive feedback provides additional
competitive dominance of buoyant cyanobac-
teria over nonbuoyant phytoplankton.
Global warming also affects patterns of
precipitation and drought. These changes in
the hydrological cycle could further enhance
cyanobacterial dominance. For example,
more intense precipitation will increase sur-
face and groundwater nutrient discharge into
water bodies. In the short term, freshwater dis-
charge may prevent blooms by flushing.
However, as the discharge subsides and water
residence time increases as a result of drought,
nutrient loads will be captured, eventually pro-
moting blooms. This scenario takes place
when elevated winter-spring rainfall and
flushing events are followed by protracted
periods of summer drought. This sequence of
A link exists between global warming and
the worldwide proliferation of harmful
cyanobacterial blooms.
Blooms Like It Hot
Hans W. Paerl
and Jef Huisman
Institute of Marine Sciences, University of North Carolina
at Chapel Hill, Morehead City, NC 28557, USA. E-mail:
Institute for Biodiversity and
Ecosystem Dynamics, University of Amsterdam, 1018 WS
Amsterdam, Netherlands. E-mail: jef.huisman@science.
Undesired blooms. Examples of large water bodies
covered by cyanobacterial blooms include the Neuse
River Estuary, North Carolina, USA (top) and Lake
Victoria, Africa (bottom).
Published by AAAS
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events has triggered massive algal blooms in
aquatic ecosystems serving critical drinking
water, fishery, and recreational needs. At-
tempts to control fluctuations in the discharge
of rivers and lakes by means of dams and
sluices may increase residence time, further
aggravating cyanobacteria-related ecological
and human health problems.
In addition, summer droughts, rising sea
levels, increased withdrawal of freshwater for
agricultural use, and application of road salt as
a deicing agent have led to rising lake
salinities in many regions. Several common
cyanobacteria are more salt-tolerant than
freshwater phytoplankton species (12, 13).
This high salt tolerance is reflected by increas-
ing reports of toxic cyanobacterial blooms in
brackish waters (2, 6).
Some cyanobacteria have substantially
expanded their geographical ranges. For
example, Cylindrospermopsis raciborskii
the species responsible for “Palm Island mys-
tery disease,” an outbreak of a severe hepati-
tis-like illness on Palm Island, Australia (4)—
was originally described as a tropical/subtrop-
ical genus. The species appeared in southern
Europe in the 1930s and colonized higher lat-
itudes in the late 20th century. It is now wide-
spread in lakes in northern Germany (14).
Similarly, the species was noted in Florida
almost 35 years ago and is now commonly
found in reservoirs and lakes experiencing
eutrophication in the U.S. southeast and mid-
west (2). It is adapted to the low-light condi-
tions that typify eutrophic waters, prefers
water temperatures above 20°C, and survives
adverse conditions through the use of special-
ized resting cells (14). These bloom character-
istics suggest a link to eutrophication and
global warming.
More detailed studies of the population
dynamics in cyanobacterial blooms are needed.
For example, competition between toxic and
nontoxic strains affects the toxicity of
cyanobacterial blooms (15). Furthermore,
viruses may attack cyanobacteria and mediate
bloom development and succession (16). It is
unclear how these processes are affected by
global warming. What is clear, however, is that
high nutrient loading, rising temperatures,
enhanced stratification, increased residence
time, and salination all favor cyanobacterial
dominance in many aquatic ecosystems. Water
managers will have to accommodate the effects
of climatic change in their strategies to combat
the expansion of cyanobacterial blooms.
1. J. Huisman, H. C. P. Matthijs, P. M. Visser, Harmful
Cyanobacteria (Springer, Dordrecht, Netherlands, 2005).
2. H. W. Paerl, R. S. Fulton III, in Ecology of Harmful Marine
Algae, E. Graneli, J. Turner, Eds. (Springer, Berlin, 2006),
pp. 95–107.
3. I. Chorus, J. Bartram, Toxic Cyanobacteria in Water
(Spon, London, 1999).
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6. S. Suikkanen, M. Laamanen, M. Huttunen, Estuar. Coast.
Shelf Sci. 71, 580 (2007).
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Univ. Press, Cambridge, 2006).
8. K. D. Jöhnk et al., Global Change Biol. 14, 495 (2008).
9. J. A. Elliott, I. D. Jones, S. J. Thackeray, Hydrobiologia
559, 401 (2006).
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Ser. 101, 1 (1993).
11. B. W. Ibelings, M. Vonk, H. F. J. Los, D. T. van der Molen,
W. M. Mooij, Ecol. Appl. 13, 1456 (2003).
12. L. Tonk, K. Bosch, P. M. Visser, J. Huisman, Aquat. Microb.
Ecol. 46, 117 (2007).
13. P. H. Moisander, E. McClinton III, H. W. Paerl, Microb.
Ecol. 43, 432 (2002).
14. C. Wiedner, J. Rücker, R. Brüggemann, B. Nixdorf,
Oecologia 152, 473 (2007).
15. W. E. A. Kardinaal et al., Aquat. Microb. Ecol. 48, 1 (2007).
16. M. Honjo et al., J. Plankton Res. 28, 407 (2006).
n 2006, Yamanaka and colleagues (1) dis-
covered that mouse fibroblasts could be
reprogrammed to a pluripotent, embry-
onic stem (ES) cell–like state by the simple
introduction of four transcription factors,
Oct4, Sox2, Klf4, and c-Myc. This finding has
since been reproduced (26) and extended to
human fibroblasts using the same cocktail of
genes (7, 8) or one composed of Oct4, Sox2,
Nanog, and Lin28 (9). These so-called “in-
duced pluripotent stem cells” (iPS cells)
appear similar to ES cells in that they can give
rise to all the cells of the body and display fun-
damental genetic and morphologic ES cell
characteristics (see the figure). The concept of
an iPS cell brings together decades of work in
the fields of ES cell biology and nuclear
reprogramming that predicted it might be pos-
sible to impose pluripotency upon a somatic
cell (10). iPS cells not only have the potential
to produce patient-specific stem cells, but
they also provide a platform to study the biol-
ogy of pluripotency and cell reprogramming.
In Science Express, Aoi et al. (11) broaden the
application of iPS cell methodology to murine
epithelial cell types, highlighting differences
when compared with reprogramming of
fibroblasts. And on page 97 of this issue,
Viswanathan et al. (12) address the role of one
of the reprogramming factors, Lin28, in regu-
lating microRNAs (miRNAs) in ES cells. The
findings of Viswanathan et al., and recent
work by Benetti et al. (13) and Sinkkonen et al.
(14), advance our knowledge of the little-
understood roles of miRNAs in ES cells.
Collectively, these studies take us closer to
understanding how ES cells maintain an
undifferentiated, self-renewing, and pluripo-
tent state, and to defining how pluripotency
can be imposed on other cell types.
To date, fibroblasts and mesenchymal
stem cells have been used to generate iPS cells
(19). A next step is to determine whether
other cell types are susceptible to reprogram-
ming. Toward this end, Aoi et al. produced iPS
cells from two epithelial cell populations,
adult mouse hepatocytes and gastric epithelial
cells, by expressing Oct4, Sox2, Klf4, and
c-Myc. Like iPS cells generated from fibro-
blasts (iPS-fibroblast), those from primary
hepatocytes (iPS-Hep) and gastric epithelial
cells (iPS-Stm) were pluripotent and gave rise
to adult and germline chimeras. However,
iPS-Hep and iPS-Stm differ from iPS-fibro-
blast cells in several important respects, indi-
cating that the dynamics of reprogramming
may not be equivalent in these cell types. For
instance, although c-Myc was used, iPS-Hep
and iPS-Stm cell–derived chimeric mice did
not display the c-Myc–dependent tumori-
genicity observed in iPS-fibroblast–derived
chimeric mice. In addition, iPS-Hep and iPS-
Stm cells could be generated using less strin-
gent selection conditions. Thus, epithelial cell
types may be more prone to reprogramming
than fibroblasts.
How do these differences inform us about
the mechanism of reprogramming? Given that
ES cells are an epithelial population, charac-
terized by cell adhesion (mediated by the
membrane protein E-cadherin), one possibil-
ity is that epithelialization is an event required
The requirements for reprogramming different
somatic cell types to a pluripotent state may
not be equivalent.
Deconstructing Pluripotency
Anne G. Bang and Melissa K. Carpenter
Novocell Inc., 3550 General Atomics Court, San Diego, CA
92121, USA. E-mail:
Published by AAAS
on April 4, 2008 www.sciencemag.orgDownloaded from
    • Among them, temperature is one of the most important factors. Cyanobacteria usually grow better at relatively high temperature compared to other phyla of phytoplankton (Paerl & Huisman 2008). This may explain why the proportion of Cyanophyta was higher in July.
    [Show abstract] [Hide abstract] ABSTRACT: Lake Taihu has attracted attention worldwide because of its extensive cyanobacterial blooms in the warm season. A better understanding of nutrient controls over phytoplankton is critical if the blooms are to be controlled. In the present study, we investigated the effects of nutrient addition on the growth of phytoplankton collected from Meiliang Bay (Station 1), Lake Center (Station 2), and Xukou Bay (Station 3) in July and September 2011. Cyanophyta was dominant in all water samples. Nevertheless, we observed higher proportions of other phyla and lower concentrations of microcystin-LR in September than in July. Further, Station 3 possessed many fewer Cyanophyta, but disproportionately higher concentrations of microcystin-LR than the other two stations. The overall phytoplankton biomass decreased in the order Station 1 > Station 2 > Station 3 and July > September. More interestingly, phosphorus-induced phytoplankton growth coincided with a distinct drop in particulate organic carbon (or nitrogen) to phosphorus ratio at Stations 2 and 3. By contrast, nitrogen, applied either alone or together with phosphorus, had negligible effect on phytoplankton growth. These results suggest that phytoplankton at Stations 2 and 3 were limited by phosphorus and no nutrient limitation occurred at Station 1. Therefore, nutrient limitation in Lake Taihu may be more dynamic and sporadic than previously thought and has implications for management of phytoplankton blooms.
    Full-text · Article · Jan 2015
    • In nature, positive associations are the rule and negative associations are uncommon (Schluter 1984, Bertness and Callaway 1994, Li et al. 2008). The loss of connections may cause an algal bloom, particularly if the algae are favored by some positive feedback, such as allelopathy and favorable environmental conditions (Paerl and Huisman 2008). In fact, allelopathy is a strategy TABLE 2. Putative identification of key and dominant bacterioplankton T-RFs by in silico restriction digestions of 16S rRNA sequences.
    [Show abstract] [Hide abstract] ABSTRACT: Algal blooms are a worldwide phenomenon and the biological interactions that underlie their regulation are only just beginning to be understood. It is established that algal microorganisms associate with many other ubiquitous, oceanic organisms, but the interactions that lead to the dynamics of bloom formation are currently unknown. To address this gap, we used network approaches to investigate the association patterns among microeukaryotes and bacterioplankton in response to a natural Scrippsiella trochoidea bloom. This is the first study to apply network approaches to bloom dynamics. To this end, terminal restriction fragment length polymorphism analysis showed dramatic changes in community compositions of microeukaryotes and bacterioplankton over the blooming period. A variance ratio test revealed significant positive overall associations both within and between microeukaryotic and bacterioplankton communities. An association network generated from significant correlations between terminal restriction fragments (T-RFs) revealed that S. trochoidea had few connections to other microeukaryotes and bacterioplankton and was placed on the edge. This lack of connectivity allowed for the S. trochoidea sub-network to break off from the overall network. These results allowed us to propose a conceptual model for explaining how changes in microbial associations regulate the dynamics of an algal bloom. In addition, key T-RFs were screened by principle component analysis, correlation coefficients and network analysis. Dominant T-RFs were then identified through 18S and 16S rRNA gene clone libraries. Results showed that microeukaryotes clustered predominantly with Dinophyceae and Perkinsea while the majority of bacterioplankton identified were Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. The ecological roles of both were discussed in the context of these findings.This article is protected by copyright. All rights reserved.
    Full-text · Article · Nov 2014
    • Cyanobacterial harmful algal blooms (CHABs) occur worldwide and their increasing prevalence has been associated with severe ecological and economic impacts across the marine-freshwater continuum [1]–[8]. Many CHAB genera include species and strains that can produce toxins and other bioactive compounds that present a risk to the health of humans and other animals [9].
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    Full-text · Article · Sep 2014
    • Anthropogenic influence on freshwater ecosystems, especially increased nutrient loading and global warming, has led to more frequently occurring cyanobacterial blooms (Dokulil and Teubner, 2000; Paerl and Huisman, 2008; O'Neil et al., 2012). Cyanobacteria in high abundances are known to have a strong impact on freshwater ecosystems; for instance by negatively affecting herbivorous zooplankton (Ghadouani et al., 2003; Wilson et al., 2006).
    [Show abstract] [Hide abstract] ABSTRACT: Cyanobacterial blooms in freshwater ecosystems are a matter of high concern with respect to human health and ecosystem services. Investigations on the role of cyanobacterial secondary metabolites have largely been confined to microcystins, although cyanobacteria produce a huge variety of toxic or inhibitory secondary metabolites. Mass occurrences of toxic cyanobacteria strongly impact freshwater zooplankton communities; especially the unselective filter feeder Daphnia. Daphnids have been shown to successfully suppress bloom formation. However, the opposite situation, i.e. the suppression of Daphnia populations by cyanobacteria can be observed as well. To understand these contradictory findings the elucidation of the underlying physiological mechanisms that help daphnids to cope with cyanotoxins is crucial.
    Full-text · Article · Aug 2014
    • This increases the possibility of sterol limitation during cyanobacteria blooms (Wacker and Martin-Creuzburg, 2007), the occurrence of which may be favoured by climate change (i.e. global warming) (Jöhnk et al., 2008; Paerl and Huisman, 2008). However, Piepho et al. (Piepho et al., 2010, 2012) suggest that the occurrence of herbivore sterol limitation might not be restricted to cyanobacterial blooms.
    [Show abstract] [Hide abstract] ABSTRACT: Daphnia responds to low availability of carbon (food quantity) or limiting concentrations of nutrients relative to carbon (C) in excess (food quality) by respectively saving or discharging C via different pathways. We investigated which kind of food limitation leads to a faster regulation in Daphnia C budgets, and whether the pre-assimilative C pathways, ingestion and faeces egestion and the post-assimilative C pathways, excretion and respiration, are regulated concurrently. Daphnia magna were exposed to dietary shifts in different food quantities or qualities; food quality was varied in terms of the essential component, cholesterol. After acclimation to the new diet ranging from 0 to 96 h, C budgets were measured by a radiotracer technique. Dietary shifts in quantity and quality caused Daphnia to quickly adjust their C budgets within 6 h, but different C pathways were affected. A shift to low food quantity reduced Daphnia respiration indicating C retention. In contrast, sudden low quality food caused increased faeces egestion to discharge excess C. Furthermore, we observed a delayed increase in excretion but no change in respiration within the time frame studied. Such time-shifted responses appear to be an appropriate means to keep the costs of physiological adjustments relatively low, which in turn would benefit Daphnia performance.
    Full-text · Article · May 2014
    • Global phosphorus gradually scarce is one of the important challenges in the 21st century [2]. Meanwhile, over enrichment phosphorus wastewater have discharged into water environment and related to eutrophication [3]. Animal manure wastewater, produced from livestock and poultry production, contains phosphate, nitrogen, carbonate, heavy metals, and chemical compounds as major constituents.
    [Show abstract] [Hide abstract] ABSTRACT: The problem of phosphorus discharge is related to environmental protection and food security. Struvite crystallization is a useful technology for phosphate recovery from wastewater. In the research, struvite crystallization process with CO2 degasification continuous U-shape reactor (CUSR) was application for phosphate recovery from animal manure wastewater. The result indicated PO43--P recovery ratio could achieve 47-53% without magnesium addition when CUSR hydraulic retention time controlled at 60 min. With extra magnesium addition, PO43--P recovery ratio could significant achieve 80-86% at magnesium addition amount 57.5 mg/dm3. PHREEQC modeling predictions trend of struvite crystallization was close to CUSR experimental results. The modeling calculation can provide a theoretical guide for operational parameters design. For seeding technology, high phosphate recovery efficiency was obtained and preformed struvite was the most effective seeding material. Surface characterization analysis demonstrated the dominant composition of chemical solids was struvite. Water extraction analysis indicated chemical solids recovery from animal manure wastewater could release PO43--P slowly and be available as slow-release fertilizer.
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July 2003 · Veterinary Research · Impact Factor: 2.82
Toxigenic cyanobacteria are photosynthetic prokaryotes that are most often recognized in marine and freshwater systems, such as lakes, ponds, rivers, and estuaries. When environmental conditions (such as light, nutrients, water column stability, etc.) are suitable for their growth, cyanobacteria may proliferate and form toxic blooms in the upper, sunlit layers. The biology and ecology of... [Show full abstract]
July 2003 · Environmental Toxicology · Impact Factor: 3.20
The freshwater cyanobacterium Cylindrospermopsis raciborskii is known to produce toxic effects in several countries. Acute and chronic exposures to C. raciborskii in Australia have been linked to liver damage (hepatotoxicity) with concomitant effects on the kidneys, adrenal glands, small intestine, lungs, thymus, and heart. The alkaloid cylindrospermopsin, which produces these toxic effects,... [Show full abstract]
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Cylindrospermopsis raciborskii, a potentially toxic blooming cyanobacterium (blue-green alga), responsible for public health problems in Australia, was identified in France in 1994 in a shallow pond south of Paris. A program monitoring the occurrence of C. raciborskii in this pond was conducted from July 1998 to October 1999. The phytoplankton assemblages were studied, and limnological... [Show full abstract]
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Plastics devices used for the field collection of water samples may contain plastics additives which will interfere with the HPLC determination of the cyanobacterial toxins microcystins. The presence of the additives resorcinol monobenzoate or 2,4-dihydroxybenzophenone can interfere with the determination of microcystin-LR. The presence of bisphenol A in plastics can interfere with the... [Show full abstract]
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