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occurred immediately after the die-off.
Several factors acting at various spatial and temporal scales
influence seagrass recovery after a disturbance. In Tampa Bay,
water clarity was the main driver preventing seagrass recovery
(Greening et al., 2011), while genetic material was the limiting
factor in the recovery of seagrass in Shark Bay, Australia
(Nowicki et al., 2017). The sequence of events (die-off > plume
extent > lack of SAV recovery) in Johnson suggests that the
seagrass seascape in Johnson entered into a feedback cycle of
degradation between seagrass cover and turbidity, preventing
recovery (Figure 1). This cycle is common within degraded
seagrass habitats and does not allow for seagrass to recover,
which is evident in Johnson. A similar pattern occurred in
seagrass beds near the Great Barrier Reef, where sediment
plumes from dredging prevented the establishment of seagrass
(York et al., 2015).
Persistent algal blooms and proximity to freshwater
inflows may also play a factor in reducing light penetration
and preventing seagrass recovery in Florida Bay. Central
Florida Bay experiences seasonal algal blooms originating
Frontiers in Marine Science \| www.frontiersin.org 9 July 2021 \| Volume 8 \| Article 633240
Rodemann et al. Sediment Plume and Seagrass Resilience
from anthropogenically altered freshwater deliveries
(Boyer et al., 2009; Briceño and Boyer, 2010) and large-scale algal
blooms brought on by tropical storms and hurricanes (Glibert
et al., 2009; Wahl, 2019). The seagrass die-off in the late 1980’s
exacerbated algal blooms in this region, leading to negative
effects on seagrass recovery (Robblee et al., 1991; Fourqurean and
Robblee, 1999). However, Hall et al. (2021) found no evidence of
algal blooms depleting sources of seagrass recruits after the 1980’s
die-off. Furthermore, freshwater inflows may be affecting the
recovery of seagrass within Florida Bay. H. wrightii, the pioneer
seagrass species, is favored over T. testudinum in lower salinity
conditions (Herbert et al., 2011). Rankin Basin is located closer
to freshwater inflows than Johnson Basin. Therefore, higher
freshwater inflows and lower salinities in Rankin Basin may have
contributed to a more rapid recovery. Further research is needed
to determine the variables affecting seagrass recovery within
Florida Bay, especially considering the hydrodynamics drivers
that interactively influenced seagrass physiology, productivity
and patch formation.
While Johnson Basin experienced high turbidity from the
sediment plume right after the die-off, suspended sediment
associated with the sediment plume did not reach Rankin until
2 years later. This delay in disturbance may have allowed Rankin
to begin recolonizing the benthos as illustrated by the recovery of
seagrass cover (by mostly H. wrightii) to a BB score of 2.5 before
the sediment plume entered Rankin. Recolonization followed
traditional models of SAV succession, wherein macroalgae
colonize the bare sediment and then H. wrightii replaces the
macroalgae (Den Hartog, 1979; Zieman, 1982). Due to the
known function of seagrass habitats for sediment stabilization
and deposition in coastal environments (Bos et al., 2007), we
hypothesize that the establishment of H. wrightii within Rankin
helped stabilize the sediment. Therefore, when Hurricane Irma
expanded the plume into Rankin, the system exhibited resistance
to the increase in turbidity and prevented the shift into the
degrading feedback loop shown in Figure 1. Furthermore, the
wind may have played a role in reducing the impact of the
sediment plume in Rankin. Southern Florida experiences strong
easterly winds in fall and winter (Klink, 1999), which may have
aided in removing the plume from Rankin after a couple of years.
Western Florida Bay, including Johnson, faces a more difficult
road to recovery. The sediment plume expanded into this region
TABLE 4 \| Analysis of variance (ANOVA) used to determine significant differences
in (a) proportion of basin covered and (b) seagrass cover between basin and
before and after the breakpoint.
Variable F1,44 p
(a) Proportion of basin covered Basin 73.2 <0.001*
Break 150.8 <0.001*
BasinBreak 32.8 <0.001
(b) Seagrass cover Basin 4.3 0.051
Break 6.7 0.018*
BasinBreak 7.2 0.014
Shown are the variable tested (Variable), test statistic of the significance (F), the
approximate p-values for the null hypotheses that there is no difference (p).
Significant values are denoted with *.
right after the 2015 die-off, preventing any SAV recovery and
driving the system into a turbid alternative state that persisted
through 2020 in our study. Recovery of seagrass after the dieoff in the late 1980’s might present a solution that includes
light availability and time. Stumpf et al. (1999) mapped albedo
throughout Florida Bay before and after the first seagrass dieoff. They found that sediment expanded into the western region
starting in 1988 and persisted through 1997 (the duration of
their time series), but lost intensity beginning in 1996. Once
this loss in intensity (reduction in turbidity) reaches a certain
threshold, benthic macroalgae can start recolonizing an area.
Benthic macroalgae only need approximately 8–10% of surface
irradiance to grow (Choice et al., 2014). Therefore, time may
be the only factor required for sediment settlement to occur,
reducing turbidity and increasing benthic light intensity to the 8–
10% threshold needed for macroalgae recolonization. Macroalgae
recolonization then has the potential to create a beneficial
feedback loop, leading to increased sediment stabilization.
If there is a source of seagrass genetic material available
(seed reserve or connectivity to clonal sources), the sediment
stabilization may result in seagrass recovery in Johnson and the
rest of western Florida Bay (Austin et al., 2017). Florida Bay
returned to pre-die-off conditions by 2012 (Hall et al., 2016),
illustrating that the system can undergo the lengthy (15 years)
recovery process. But it is unknown whether there are enough

occurred immediately after the die-off.

Several factors acting at various spatial and temporal scales

influence seagrass recovery after a disturbance. In Tampa Bay,

water clarity was the main driver preventing seagrass recovery

(Greening et al., 2011), while genetic material was the limiting

factor in the recovery of seagrass in Shark Bay, Australia

(Nowicki et al., 2017). The sequence of events (die-off > plume

extent > lack of SAV recovery) in Johnson suggests that the

seagrass seascape in Johnson entered into a feedback cycle of

degradation between seagrass cover and turbidity, preventing

recovery (Figure 1). This cycle is common within degraded

seagrass habitats and does not allow for seagrass to recover,

which is evident in Johnson. A similar pattern occurred in

seagrass beds near the Great Barrier Reef, where sediment

plumes from dredging prevented the establishment of seagrass

(York et al., 2015).

Persistent algal blooms and proximity to freshwater

inflows may also play a factor in reducing light penetration

and preventing seagrass recovery in Florida Bay. Central

Florida Bay experiences seasonal algal blooms originating

Frontiers in Marine Science | www.frontiersin.org 9 July 2021 | Volume 8 | Article 633240

Rodemann et al. Sediment Plume and Seagrass Resilience

from anthropogenically altered freshwater deliveries

(Boyer et al., 2009; Briceño and Boyer, 2010) and large-scale algal

blooms brought on by tropical storms and hurricanes (Glibert

et al., 2009; Wahl, 2019). The seagrass die-off in the late 1980’s

exacerbated algal blooms in this region, leading to negative

effects on seagrass recovery (Robblee et al., 1991; Fourqurean and

Robblee, 1999). However, Hall et al. (2021) found no evidence of

algal blooms depleting sources of seagrass recruits after the 1980’s

die-off. Furthermore, freshwater inflows may be affecting the

recovery of seagrass within Florida Bay. H. wrightii, the pioneer

seagrass species, is favored over T. testudinum in lower salinity

conditions (Herbert et al., 2011). Rankin Basin is located closer

to freshwater inflows than Johnson Basin. Therefore, higher

freshwater inflows and lower salinities in Rankin Basin may have

contributed to a more rapid recovery. Further research is needed

to determine the variables affecting seagrass recovery within

Florida Bay, especially considering the hydrodynamics drivers

that interactively influenced seagrass physiology, productivity

and patch formation.

While Johnson Basin experienced high turbidity from the

sediment plume right after the die-off, suspended sediment

associated with the sediment plume did not reach Rankin until

2 years later. This delay in disturbance may have allowed Rankin

to begin recolonizing the benthos as illustrated by the recovery of

seagrass cover (by mostly H. wrightii) to a BB score of 2.5 before

the sediment plume entered Rankin. Recolonization followed

traditional models of SAV succession, wherein macroalgae

colonize the bare sediment and then H. wrightii replaces the

macroalgae (Den Hartog, 1979; Zieman, 1982). Due to the

known function of seagrass habitats for sediment stabilization

and deposition in coastal environments (Bos et al., 2007), we

hypothesize that the establishment of H. wrightii within Rankin

helped stabilize the sediment. Therefore, when Hurricane Irma

expanded the plume into Rankin, the system exhibited resistance

to the increase in turbidity and prevented the shift into the

degrading feedback loop shown in Figure 1. Furthermore, the

wind may have played a role in reducing the impact of the

sediment plume in Rankin. Southern Florida experiences strong

easterly winds in fall and winter (Klink, 1999), which may have

aided in removing the plume from Rankin after a couple of years.

Western Florida Bay, including Johnson, faces a more difficult

road to recovery. The sediment plume expanded into this region

TABLE 4 | Analysis of variance (ANOVA) used to determine significant differences

in (a) proportion of basin covered and (b) seagrass cover between basin and

before and after the breakpoint.

Variable F1,44 p

(a) Proportion of basin covered Basin 73.2 <0.001*

Break 150.8 <0.001*

Basin*Break 32.8 <0.001*

(b) Seagrass cover Basin 4.3 0.051

Break 6.7 0.018*

Basin*Break 7.2 0.014*

Shown are the variable tested (Variable), test statistic of the significance (F), the

approximate p-values for the null hypotheses that there is no difference (p).

Significant values are denoted with *.

right after the 2015 die-off, preventing any SAV recovery and

driving the system into a turbid alternative state that persisted

through 2020 in our study. Recovery of seagrass after the dieoff in the late 1980’s might present a solution that includes

light availability and time. Stumpf et al. (1999) mapped albedo

throughout Florida Bay before and after the first seagrass dieoff. They found that sediment expanded into the western region

starting in 1988 and persisted through 1997 (the duration of

their time series), but lost intensity beginning in 1996. Once

this loss in intensity (reduction in turbidity) reaches a certain

threshold, benthic macroalgae can start recolonizing an area.

Benthic macroalgae only need approximately 8–10% of surface

irradiance to grow (Choice et al., 2014). Therefore, time may

be the only factor required for sediment settlement to occur,

reducing turbidity and increasing benthic light intensity to the 8–

10% threshold needed for macroalgae recolonization. Macroalgae

recolonization then has the potential to create a beneficial

feedback loop, leading to increased sediment stabilization.

If there is a source of seagrass genetic material available

(seed reserve or connectivity to clonal sources), the sediment

stabilization may result in seagrass recovery in Johnson and the

rest of western Florida Bay (Austin et al., 2017). Florida Bay

returned to pre-die-off conditions by 2012 (Hall et al., 2016),

illustrating that the system can undergo the lengthy (15 years)

recovery process. But it is unknown whether there are enough