patrickbdevaney/mia9 · Datasets at Hugging Face

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seagrass loss and further sediment resuspension (Nyström et al.,
2012; Maxwell et al., 2017; O’Brien et al., 2017; Figure 1).
How seagrass ecosystems respond to these external
disturbances is dependent upon the frequency and severity
of the disturbance (O’Brien et al., 2017). Strong, or frequent
disturbances can result in regime shifts, or a change from one
ecosystem state to another, at the spatial scale of the disturbance
(Nyström et al., 2012; O’Brien et al., 2017). For example, removal
of seagrass due to propeller scarring changes the ecosystem state
within the width of the scar (often <1 m) from vegetated to
unvegetated. Without further disturbance, the seagrass recovers
within a year and reaches the original ecosystem state within
6 years (Dawes et al., 1997; Kenworthy et al., 2002). However,
if the disturbance is severe or frequent enough, ecosystems can
become locked into a degraded state through the creation of
new stabilizing feedbacks. If the destabilizing feedback loops are
strong enough, the system will experience a lag in recovery (i.e.,
hysteresis) and may enter an alternative stable state (Scheffer
et al., 2001; Beisner et al., 2003; Petraitis et al., 2009; Nyström
et al., 2012).
Seagrass ecosystems are particularly vulnerable to changes
into alternative stable states due to the number and strength
of feedbacks within these systems (Maxwell et al., 2017). One
example of the long-term impact that hysteresis can have on
a seagrass ecosystem is the Dutch Wadden Sea (Scheffer et al.,
2001; van der Heide et al., 2007). The construction of a large
dam and a seagrass wasting disease in the 1930s resulted in the
collapse of large eelgrass (Zostera marina) meadows, which led
to an unvegetated, turbid alternative stable state that still persists
despite restoration efforts (van Katwijk and Hermus, 2000; van
Katwijk et al., 2000; van der Heide et al., 2007). Unfortunately,
the number of coastal ecosystems experiencing shifts to degraded
alternative stable states has risen since the mid 20th century
(Duarte et al., 2009; Carstensen et al., 2011; Maxwell et al., 2017).
Proper management of coastal ecosystems, specifically seagrass
ecosystems, requires more information on the causes and impacts
of such regime shifts.
Florida Bay, the estuary between the Florida mainland and the
Florida Keys, has a long history of anthropogenic and natural
disturbances, including the reduction of freshwater inputs from
water management practices, altered water circulation associated
with the completion of the Flagler Over-Sea Railroad in 1912,
and a number of hurricanes and tropical storms (Fourqurean
and Robblee, 1999). Such disturbances have resulted in a reduced
exchange between Florida Bay and the Atlantic Ocean, increased
water residence time, changes in water circulation patterns,
higher salinities, more frequent algal blooms, and decreased
seagrass diversity (i.e., an increase in Thalassia testudinumdominated communities, Rudnick et al., 2005; Madden et al.,
2009). A combination of high bottom water temperatures,
hypersalinity and prolonged bottom water anoxia caused a largescale seagrass die-off between 1987 and 1991 that affected 27,000
ha of T. testudinum, and led to loss of submerged aquatic
vegetation (SAV) coverage, increased water column production
and turbidity, and trophic shifts (Robblee et al., 1991; Fourqurean
and Robblee, 1999). After nearly a decade of persistent algal
blooms, the system required an additional 6–10 years to return
to pre-die-off levels of T. testudinum coverage (Hall et al., 2016).
However, a second drought-induced seagrass die-off occurred
in 2015, leading to another potential regime shift (Hall et al.,
2016; Figure 2). The region was disturbed again in 2017, when
Hurricane Irma passed through Florida Bay as a category 4
hurricane, impacting areas of Florida Bay and the Florida Keys
(Wilson et al., 2020; Figure 2). Large and frequent disturbance
events such as these could induce a state of turbidity that
influences the growth and stability of seagrass habitats (Figure 1).
In this article, we describe the expansion of a heretofore
undocumented sediment plume in the western region of Florida
Bay in relation to these two recent disturbances: the 2015
seagrass die-off and Hurricane Irma in 2017. Furthermore,
we investigate the potential interaction of the sediment plume
with seagrass recovery. Using a remote sensing approach, we
addressed the following questions: (a) To what extent did the
sediment plume expand after each of the two disturbances (pre
vs. post comparisons)? (b) Which disturbance had a greater effect
on the expanse of the plume? and (c) Is there an interaction
between sediment plume coverage and changes in seagrass cover?
We addressed these questions by delineating changes in plume
extent over 2008–2020 and in relation to the timing of the two
disturbances using satellite imagery. We then compared changes
in plume extent relative to long term seagrass cover data across
two focal basins of interest, Johnson and Rankin, both affected
and undergoing recovery from the 2015 seagrass event. Based
Frontiers in Marine Science \| www.frontiersin.org 2 July 2021 \| Volume 8 \| Article 633240
Rodemann et al. Sediment Plume and Seagrass Resilience
FIGURE 1 \| Conceptual diagram illustrating the turbidity feedback loop within Florida Bay seagrass ecosystems. Two large disturbances (a 2015 seagrass die-off
and the 2017 Hurricane Irma) caused a reduction in seagrass cover, which increased sediment mobility and thus, the amount of sediment in the water column,
which in turn decreased light penetration while increasing turbidity and burial (Figure adapted from Nyström et al., 2012).
on these data, we discuss the potential impact of this expanding
sediment plume on seagrass communities throughout Florida
Bay and what to expect in the future.
MATERIALS AND METHODS
Study Site
Florida Bay is the largest estuary in Florida (2,200 km2
), located
at the southern end of the Florida peninsula and of Everglades
National Park (ENP, Figure 2). The bay consists of a patchwork
of shallow interconnected basins (1–2 m depth), mud banks
(<0.5 m depth), seagrass meadows, mangrove islands, and
narrow tidal channels. Florida Bay has restricted water exchange
and high residence time, which can make regions of the bay
prone to hypersalinity (Nuttle et al., 2000; Rudnick et al., 2005).

seagrass loss and further sediment resuspension (Nyström et al.,

2012; Maxwell et al., 2017; O’Brien et al., 2017; Figure 1).

How seagrass ecosystems respond to these external

disturbances is dependent upon the frequency and severity

of the disturbance (O’Brien et al., 2017). Strong, or frequent

disturbances can result in regime shifts, or a change from one

ecosystem state to another, at the spatial scale of the disturbance

(Nyström et al., 2012; O’Brien et al., 2017). For example, removal

of seagrass due to propeller scarring changes the ecosystem state

within the width of the scar (often <1 m) from vegetated to

unvegetated. Without further disturbance, the seagrass recovers

within a year and reaches the original ecosystem state within

6 years (Dawes et al., 1997; Kenworthy et al., 2002). However,

if the disturbance is severe or frequent enough, ecosystems can

become locked into a degraded state through the creation of

new stabilizing feedbacks. If the destabilizing feedback loops are

strong enough, the system will experience a lag in recovery (i.e.,

hysteresis) and may enter an alternative stable state (Scheffer

et al., 2001; Beisner et al., 2003; Petraitis et al., 2009; Nyström

et al., 2012).

Seagrass ecosystems are particularly vulnerable to changes

into alternative stable states due to the number and strength

of feedbacks within these systems (Maxwell et al., 2017). One

example of the long-term impact that hysteresis can have on

a seagrass ecosystem is the Dutch Wadden Sea (Scheffer et al.,

2001; van der Heide et al., 2007). The construction of a large

dam and a seagrass wasting disease in the 1930s resulted in the

collapse of large eelgrass (Zostera marina) meadows, which led

to an unvegetated, turbid alternative stable state that still persists

despite restoration efforts (van Katwijk and Hermus, 2000; van

Katwijk et al., 2000; van der Heide et al., 2007). Unfortunately,

the number of coastal ecosystems experiencing shifts to degraded

alternative stable states has risen since the mid 20th century

(Duarte et al., 2009; Carstensen et al., 2011; Maxwell et al., 2017).

Proper management of coastal ecosystems, specifically seagrass

ecosystems, requires more information on the causes and impacts

of such regime shifts.

Florida Bay, the estuary between the Florida mainland and the

Florida Keys, has a long history of anthropogenic and natural

disturbances, including the reduction of freshwater inputs from

water management practices, altered water circulation associated

with the completion of the Flagler Over-Sea Railroad in 1912,

and a number of hurricanes and tropical storms (Fourqurean

and Robblee, 1999). Such disturbances have resulted in a reduced

exchange between Florida Bay and the Atlantic Ocean, increased

water residence time, changes in water circulation patterns,

higher salinities, more frequent algal blooms, and decreased

seagrass diversity (i.e., an increase in Thalassia testudinumdominated communities, Rudnick et al., 2005; Madden et al.,

2009). A combination of high bottom water temperatures,

hypersalinity and prolonged bottom water anoxia caused a largescale seagrass die-off between 1987 and 1991 that affected 27,000

ha of T. testudinum, and led to loss of submerged aquatic

vegetation (SAV) coverage, increased water column production

and turbidity, and trophic shifts (Robblee et al., 1991; Fourqurean

and Robblee, 1999). After nearly a decade of persistent algal

blooms, the system required an additional 6–10 years to return

to pre-die-off levels of T. testudinum coverage (Hall et al., 2016).

However, a second drought-induced seagrass die-off occurred

in 2015, leading to another potential regime shift (Hall et al.,

2016; Figure 2). The region was disturbed again in 2017, when

Hurricane Irma passed through Florida Bay as a category 4

hurricane, impacting areas of Florida Bay and the Florida Keys

(Wilson et al., 2020; Figure 2). Large and frequent disturbance

events such as these could induce a state of turbidity that

influences the growth and stability of seagrass habitats (Figure 1).

In this article, we describe the expansion of a heretofore

undocumented sediment plume in the western region of Florida

Bay in relation to these two recent disturbances: the 2015

seagrass die-off and Hurricane Irma in 2017. Furthermore,

we investigate the potential interaction of the sediment plume

with seagrass recovery. Using a remote sensing approach, we

addressed the following questions: (a) To what extent did the

sediment plume expand after each of the two disturbances (pre

vs. post comparisons)? (b) Which disturbance had a greater effect

on the expanse of the plume? and (c) Is there an interaction

between sediment plume coverage and changes in seagrass cover?

We addressed these questions by delineating changes in plume

extent over 2008–2020 and in relation to the timing of the two

disturbances using satellite imagery. We then compared changes

in plume extent relative to long term seagrass cover data across

two focal basins of interest, Johnson and Rankin, both affected

and undergoing recovery from the 2015 seagrass event. Based

Frontiers in Marine Science | www.frontiersin.org 2 July 2021 | Volume 8 | Article 633240

Rodemann et al. Sediment Plume and Seagrass Resilience

FIGURE 1 | Conceptual diagram illustrating the turbidity feedback loop within Florida Bay seagrass ecosystems. Two large disturbances (a 2015 seagrass die-off

and the 2017 Hurricane Irma) caused a reduction in seagrass cover, which increased sediment mobility and thus, the amount of sediment in the water column,

which in turn decreased light penetration while increasing turbidity and burial (Figure adapted from Nyström et al., 2012).

on these data, we discuss the potential impact of this expanding

sediment plume on seagrass communities throughout Florida

Bay and what to expect in the future.

MATERIALS AND METHODS

Study Site

Florida Bay is the largest estuary in Florida (2,200 km2

), located

at the southern end of the Florida peninsula and of Everglades

National Park (ENP, Figure 2). The bay consists of a patchwork

of shallow interconnected basins (1–2 m depth), mud banks

(<0.5 m depth), seagrass meadows, mangrove islands, and

narrow tidal channels. Florida Bay has restricted water exchange

and high residence time, which can make regions of the bay

prone to hypersalinity (Nuttle et al., 2000; Rudnick et al., 2005).