the input of sediments and sea-level trends, the accumulation of sediments (sands or gravels) leads to continuous
progradation of the coastline towards the detached
obstacle (usually an island). A smaller sediment protrusion can also be developed in the back side of the obstacle.
The final phase of this process is the complete coalescence
between these sediment features and the blockage of the
water body located behind the obstacle, with the consequent formation of a connection between the obstacle
and the mainland (i.e., the tombolo). Tombolos can be
classified as simple, when the feature is formed by
a single sediment body, or complex (doubles, triples,
etc.), in which the sediment ridges can be formed in
a different time (Johnson and Reed, 1910). In this last
case, lagoons can be formed between ridges, marking
intervals of interruption of the tombolo formation.
Bibliography
Johnson, D. W., and Reed, W. G., Jr., 1910. The form of Nantasket
beach. Journal of Geology, 18, 162–189.
Cross-references
Coastal Lagoons
Coastal Landforms
Shoreline
TOXIC BLOOMS
Kevin G. Sellner
Chesapeake Research Consortium, Edgewater, MD, USA
Synonyms
Allelopathic algae; Harmful algal blooms (HABs);
High-biomass blooms; “Red tides”
Definition
Toxic blooms are the accumulation of toxin-producing
cells that lead to aquatic living resource mortalities or illness or deaths in avian or terrestrial mammals, including
humans.
Mortalities from blooms can also occur through indirect
effects of the accumulation of high biomass typical of
blooms and the subsequent respiration or death and
decomposition that consumes the available oxygen, leading to suffocation and dying and dead fauna.
Introduction
Toxin-producing taxa and syndromes
Toxic blooms are generally accumulations of phytoplankton (microscopic single-cell free-floating plants) and
occasionally mixotrophic or heterotrophic dinoflagellates,
benthic dinoflagellates, or macroalgae. Some of the cells
accumulating produce complex intracellular compounds
that are toxic to various freshwater and marine fauna as
well as higher organisms that include birds and
mammals. The suite of toxins produced (http://www.
issha.org/Welcome-to-ISSHA/Harmful-Algae-Links) has
a primary toxin and then many substituted congeners
and include paralytic shellfish poisons (PSP), primarily
from saxitoxin and gonyautoxins and their derivatives in
marine dinoflagellates like Alexandrium species and
others; neurotoxic shellfish poisons (NSP) such as
brevetoxin produced by Karenia brevis in Florida red tides
and anatoxin from some freshwater cyanobacteria;
domoic acid for amnesic shellfish poisons (ASP) produced by some marine members of the diatom genus
Pseudo-nitzschia; ciquatera fish poisons (CFP) from toxin
precursors for ciguatoxins and maitotoxins produced by
some benthic marine dinoflagellate species like
Gambierdiscus; diarrhetic shellfish poisons (DSP) from
okadaic acid produced by the marine dinoflagellate
Dinophysis and ichthyotoxic karlotoxins from the brackish dinoflagellate Karlodinium, which kill many fish and
dramatically reduce grazing pressures from small planktonic grazers; azaspiracids which induce vomiting and
diarrhea, produced from the marine dinoflagellate
Azadinium spinosum; and the hepatotoxic microcystins
produced by Microcystis and other freshwater
cyanobacteria. Other toxins (prymnesins, nodularin,
yessotoxin, palytoxins, tetrodotoxin, spirolides) are also
found less frequently throughout the world. Exposure for
most birds and mammals is primarily through shellfish
and other organisms that concentrate toxic cells and are
subsequently ingested by the larger consumers, including
humans; drinking water supplies may also be toxin
sources for some of the freshwater toxins. Distributions
of these toxins and bloom formers can be viewed at
http://www.whoi.edu/redtide/regions/world-distribution.
High-biomass blooms
Toxin- and nontoxin-producing populations of the plankton and macroalgae noted above can accumulate to such
high levels that the oxygen demand associated with the
very abundant organisms can consume all available
oxygen in surrounding waters, posing serious threats to
aerobic populations of fish, shellfish, and many benthic
taxa. These high-biomass blooms are increasingly common to estuaries, and shallow coastal lagoons receiving
high nutrient loads (see Anderson et al., 2002; Heisler
et al., 2008) and bloom formers include Microcystis and
Anabaena, Prorocentrum, Ceratium, Cochlodinium
polykrikoides, raphidophytes, pelagophytes (brown tides),
and other HAB species. Dense beds or scoured
macroalgae can also occur, leading to high respiratory
demand during decomposition and oxygen-poor conditions that threaten coexisting fauna. Finally, spring diatom
blooms can be very large in temperate estuaries where
post-bloom deposition and decomposition lead to hypoxia
or anoxia in bottom waters (e.g., Chesapeake Bay, Kemp
and Boynthon, 1992); Asian countries typically include
diatoms in lists of HABs from regional waters.
714
TOXIC BLOOMS
progradation of the coastline towards the detached
obstacle (usually an island). A smaller sediment protrusion can also be developed in the back side of the obstacle.
The final phase of this process is the complete coalescence
between these sediment features and the blockage of the
water body located behind the obstacle, with the consequent formation of a connection between the obstacle
and the mainland (i.e., the tombolo). Tombolos can be
classified as simple, when the feature is formed by
a single sediment body, or complex (doubles, triples,
etc.), in which the sediment ridges can be formed in
a different time (Johnson and Reed, 1910). In this last
case, lagoons can be formed between ridges, marking
intervals of interruption of the tombolo formation.
Bibliography
Johnson, D. W., and Reed, W. G., Jr., 1910. The form of Nantasket
beach. Journal of Geology, 18, 162–189.
Cross-references
Coastal Lagoons
Coastal Landforms
Shoreline
TOXIC BLOOMS
Kevin G. Sellner
Chesapeake Research Consortium, Edgewater, MD, USA
Synonyms
Allelopathic algae; Harmful algal blooms (HABs);
High-biomass blooms; “Red tides”
Definition
Toxic blooms are the accumulation of toxin-producing
cells that lead to aquatic living resource mortalities or illness or deaths in avian or terrestrial mammals, including
humans.
Mortalities from blooms can also occur through indirect
effects of the accumulation of high biomass typical of
blooms and the subsequent respiration or death and
decomposition that consumes the available oxygen, leading to suffocation and dying and dead fauna.
Introduction
Toxin-producing taxa and syndromes
Toxic blooms are generally accumulations of phytoplankton (microscopic single-cell free-floating plants) and
occasionally mixotrophic or heterotrophic dinoflagellates,
benthic dinoflagellates, or macroalgae. Some of the cells
accumulating produce complex intracellular compounds
that are toxic to various freshwater and marine fauna as
well as higher organisms that include birds and
mammals. The suite of toxins produced (http://www.
issha.org/Welcome-to-ISSHA/Harmful-Algae-Links) has
a primary toxin and then many substituted congeners
and include paralytic shellfish poisons (PSP), primarily
from saxitoxin and gonyautoxins and their derivatives in
marine dinoflagellates like Alexandrium species and
others; neurotoxic shellfish poisons (NSP) such as
brevetoxin produced by Karenia brevis in Florida red tides
and anatoxin from some freshwater cyanobacteria;
domoic acid for amnesic shellfish poisons (ASP) produced by some marine members of the diatom genus
Pseudo-nitzschia; ciquatera fish poisons (CFP) from toxin
precursors for ciguatoxins and maitotoxins produced by
some benthic marine dinoflagellate species like
Gambierdiscus; diarrhetic shellfish poisons (DSP) from
okadaic acid produced by the marine dinoflagellate
Dinophysis and ichthyotoxic karlotoxins from the brackish dinoflagellate Karlodinium, which kill many fish and
dramatically reduce grazing pressures from small planktonic grazers; azaspiracids which induce vomiting and
diarrhea, produced from the marine dinoflagellate
Azadinium spinosum; and the hepatotoxic microcystins
produced by Microcystis and other freshwater
cyanobacteria. Other toxins (prymnesins, nodularin,
yessotoxin, palytoxins, tetrodotoxin, spirolides) are also
found less frequently throughout the world. Exposure for
most birds and mammals is primarily through shellfish
and other organisms that concentrate toxic cells and are
subsequently ingested by the larger consumers, including
humans; drinking water supplies may also be toxin
sources for some of the freshwater toxins. Distributions
of these toxins and bloom formers can be viewed at
http://www.whoi.edu/redtide/regions/world-distribution.
High-biomass blooms
Toxin- and nontoxin-producing populations of the plankton and macroalgae noted above can accumulate to such
high levels that the oxygen demand associated with the
very abundant organisms can consume all available
oxygen in surrounding waters, posing serious threats to
aerobic populations of fish, shellfish, and many benthic
taxa. These high-biomass blooms are increasingly common to estuaries, and shallow coastal lagoons receiving
high nutrient loads (see Anderson et al., 2002; Heisler
et al., 2008) and bloom formers include Microcystis and
Anabaena, Prorocentrum, Ceratium, Cochlodinium
polykrikoides, raphidophytes, pelagophytes (brown tides),
and other HAB species. Dense beds or scoured
macroalgae can also occur, leading to high respiratory
demand during decomposition and oxygen-poor conditions that threaten coexisting fauna. Finally, spring diatom
blooms can be very large in temperate estuaries where
post-bloom deposition and decomposition lead to hypoxia
or anoxia in bottom waters (e.g., Chesapeake Bay, Kemp
and Boynthon, 1992); Asian countries typically include
diatoms in lists of HABs from regional waters.
714
TOXIC BLOOMS