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Fishery Bulletin 120(2) 
the microbiome in the human gut (Cénit et al., 2014). The 
microbiome of sponges can be equivalent to 40% of sponge 
wet body weight (Lavy et al., 2016), and high densities 
of microbes confer multiple beneficial functions, includ- 
ing access to microbially mediated metabolic pathways 
(Hentschel et al., 2006; Weisz, 2006; Schlappy et al., 2010; 
Webster and Taylor, 2012; Poppell et al., 2014). 
The gill-oxygen limitation theory, which building on 
Equations 3-6, is structured around the constraints 
resulting from a 2-D oxygen system having to supply the 
3-D bodies of water-breathing animals (Pauly and Cheung, 
2017; Pauly, 2019a, 2021a), may also apply to sponges—at 
least to high-microbial-abundance sponges with approxi- 
mately spherical shapes. 
But not all sponges are spherical. Indeed, among their 
various morphologies are tube-shaped sponges, vase-shaped 
sponges, encrusting sponges, and irregularly shaped glob- 
ular sponges. Their internal structure is equally variable. 
The internal tissues of some are dense, whereas the exten- 
sive canal system of others makes them full of voids. There 
are also striking differences in the skeletal structure and 
makeup of spicules that define in large part sponge fam- 
ilies. All of these characteristics play a role in water flow 
through sponges and influence oxygen availability. 
In addition to an illustration of the gill-oxygen limita- 
tion theory, we can now consider sponges more completely 
in the context of ecosystem functioning. Prior to this con- 
tribution, it was difficult to accurately convert the dry 
weight of wool sponges into wet weight. Without these con- 
versions, one cannot fully understand the ecological con- 
sequences of the historical collapse of the sponge fishery 
throughout the Americas in the early part of the 20th cen- 
tury, a fishery that to this day has never fully recovered 
(Stuart, 1948; McClenachan, 2008; Oronti et al., 2012). 
The commercial export of sponges in the Americas 
began in The Bahamas in 1841 with the shipwreck in 
The Bahamas of a French merchant who later carried 
500-600 specimens to Paris, where he sold them (Corfield, 
1938; Stuart, 1948). Note, however, that prior to this ship- 
ment, the merchant observed “a great number of sponges in 
use among the natives” in The Bahamas, suggesting that 
a market for sponges might have already existed there 
locally before the first exports to Europe (Corfield, 1938). 
Additionally, Moore (1910) notes that in the Florida Keys 
“li|t is known that long before these [i.e., sponges] became 
an article of commerce they [i.e., sponges] were in limited 
domestic use among the inhabitants.” It is unclear when 
exactly sponges were first harvested in the Americas. How- 
ever, it is well documented that following the first commer- 
cial export of sponges from The Bahamas in the mid-1800s, 
the large-scale export of sponges quickly spread throughout 
the Western Atlantic region, with Tarpon Springs in Florida 
and Batabano in Cuba becoming areas of major importance 
(Moore, 1910; Corfield, 1938; Bethell, 2017). 
The rise and collapse of the sponge fishery in The Bahamas 
in many ways mirrors the events that occurred throughout 
the Western Atlantic region (Stuart, 1948; McClenachan, 
2008; Oronti et al., 2012). At its peak in 1917, the industry 
employed one-third of the Bahamian workforce and included 
the harvesting, processing, and trading of sponges (Oronti 
et al., 2012; Bethell, 2017). However, by the late 1930s, a 
combination of disease, hurricanes, and overexploitation led 
to orders of magnitude decline in catches, so that by 1947, 
sponge exports had plummeted to 14.8 metric tons (Oronti 
et al., 2012). Of note is a fungal blight in the late 1930s that 
killed 70-95% of the already drastically reduced popula- 
tions of sponges in The Bahamas before spreading to adja- 
cent countries (Galtsoff et al., 1939). Beginning in the early 
1990s, repeated phytoplankton blooms similarly destroyed 
up to 95% of the sponge communities over large swaths of the 
Florida Keys, where commercial sponge fishing continues to 
this day (Butler et al., 1995; Wall et al., 2012). The conversion 
from dry weight to wet weight that we present for the wool 
sponge, which was (and still is) a regionally abundant spe- 
cies and a commercially valuable species in the global trade 
(Moore, 1910; Corfield, 1938; Stuart, 1948; McClenachan, 
2008), allows the quantification of the effect of the collapse of 
the sponge fishery in the Western Atlantic Ocean on patterns 
of past ecosystem biomass-dependent functions. 
Conclusions 
The contention, herein illustrated with the wool sponge, 
that the growth of large, near-spherical sponges may 
be limited by the oxygen supply to their interior allows 
a number of inferences on their likely response to ocean 
warming and deoxygenation, and these inferences should 
be important to sponge fisheries and aquaculture and to 
the study of sponges in their ecosystem context. 
Moreover, we demonstrate that the gill-oxygen limita- 
tion theory, developed mainly with data for vertebrate, 
molluscan, and arthropod WBE, also applies to compact, 
near-spherical sponges. This demonstration provides a new 
avenue for their study, as it should allow the formulation 
of various hypotheses about their biology, notably on their 
shape-shifting past certain sizes, that should be straight- 
forward to test. 
Acknowledgments 
We thank J. Butler for the photographs in Figure 1, E. Chu 
for Figures 2—4, and J. Guitton for extraction of informa- 
tion from EcoBase. 
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