\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[ngerman,english]{babel}



\usepackage{float}








\begin{document}

\title{Arctic kelp forest decline -- a consequence of melting glaciers?}



\author[1]{Luisa Düsedau}%
\author[2]{Stein Fredriksen}%
\author[1]{Markus Brand}%
\author[1]{Philipp Fischer}%
\author[3]{Ulf Karsten}%
\author[4]{Kai Bischof}%
\author[5]{Amanda  Savoie}%
\author[1]{Inka Bartsch}%
\affil[1]{Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research}%
\affil[2]{University of Oslo}%
\affil[3]{University of Rostock Institute of Biological Sciences}%
\affil[4]{University of Bremen Faculty 2 Biology Chemistry}%
\affil[5]{Canadian Museum of Nature}%


\vspace{-1em}



  
  \date{May 25, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
The Arctic archipelago of Svalbard is a hotspot of global warming and
many fjords experience a continuous increase in seawater temperature and
glacial melt while sea-ice cover declines. In 1996/98 and 2012-14
macroalgal biomass and species diversity were quantified at the study
site Hansneset, Kongsfjorden (W-Spitsbergen) in order to identify
potential changes over time. In 2021, we repeated the earlier studies by
stratified random sampling (1x1 m2, n=3) along a sublittoral depth
transect (0, 2.5, 5, 10 and 15m) and investigated the lower depth limits
of dominant brown algae between 2-20m. The fresh weight maximum was 11.5
kg m-2 at 2.5m and kelp blades stored 277g carbon m-2 and 18g nitrogen
m-2 at this depth. Although biomass did not significantly change since
2012/13, the `Digitate Kelps' community (Laminaria digitata/Hedophyllum
nigripes) changed to an Alaria esculenta dominated kelp forest in 2021
and a balanced age structure of kelps (juveniles plus many older kelp
individuals) was only apparent at 2.5m. In addition, the abundances and
lower depth limits of all dominant brown algae declined noticeably over
the last 25 years while the deep red algae flora remained stable. As we
revealed that biomass allocation to blades, stipes and holdfasts as well
as the ability to store blade carbon and nitrogen was kelp
species-specific, a pronounced shift in the functionality of the kelp
forest had occurred over time. We propose that the observed changes in
the macroalgal community are mainly driven by alterations in underwater
light climate as in situ data confirmed increasing turbidity and
decreasing irradiance since 2012 and 2017, respectively. As a
consequence, the overall retreat of the kelp forest to lower depth
levels seems to be a result of strong glacial melt and will possibly
continue in future with unforeseen consequences for Arctic coasts and
their socio-ecological fjord systems.%
\end{abstract}%



\sloppy


\textbf{Title page}

\textbf{Arctic kelp forest decline -- a consequence of melting
glaciers?}

\selectlanguage{ngerman}\textbf{Luisa Düsedau\textsuperscript{1,4}*, Stein Fredriksen
\textsuperscript{2}, Markus Brand \textsuperscript{1}, Philipp Fischer
\textsuperscript{1}, Ulf Karsten \textsuperscript{3}, Kai Bischof
\textsuperscript{4}, Amanda Savoie \textsuperscript{5} and Inka Bartsch
\textsuperscript{1}}

\textsuperscript{1} Alfred Wegener Institute Helmholtz Centre for Polar
and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany

\textsuperscript{2} Department of Biosciences, University of Oslo, P.O.
Box 1066 Blindern, 0316 Oslo, Norway

\textsuperscript{3} Department of Applied Ecology and Phycology,
Institute of Biological Sciences, University of Rostock,
Albert-Einstein-Str. 3, 18059 Rostock, Germany

\textsuperscript{4} Marine Botany, University of Bremen \& MARUM,
James-Watt-Str. 1, 28359 Bremen, Germany

\textsuperscript{5} Centre for Arctic Knowledge and Exploration,
Canadian Museum of Nature, 240 McLeod St., K2P 2R1 Ottawa, Ontario,
Canada

\textbf{*} Corresponding author: luisa.duesedau@awi.de; +49 471 4831
1531

\textbf{Abstract}

The Arctic archipelago of Svalbard is a hotspot of global warming and
many fjords experience a continuous increase in seawater temperature and
glacial melt while sea-ice cover decline. In 1996/98 and 2012-14
macroalgal biomass and species diversity were quantified at study
siteHansneset, Kongsfjorden (W-Spitsbergen) in order to identify
potential changes over time. In 2021, we repeated the earlier studies by
stratified random sampling (1x1 m\textsuperscript{2}, n=3) along a
sublittoral depth transect (0, 2.5, 5, 10 and 15m) and investigated the
lower depth limits of dominant brown algae 220m. The fresh weight
maximum was 11.5 kg m\textsuperscript{-2} at 2.5m and kelp blades stored
277g carbon m\textsuperscript{-2} and 18g nitrogen
m\textsuperscript{-2}at this depth. Although biomass did not
significantly change since 2012/13, the `Digitate Kelps' community
(\emph{Laminaria digitata} /\emph{Hedophyllum nigripes} ) changed to an
\emph{Alaria esculenta} dominated kelp forest in 2021 and a balanced age
structure of kelps (juveniles plus many older kelp individuals) was only
apparent at 2.5m. In addition, the abundances and lower depth limits of
all dominant brown algae declined noticeably over the last 25 years
while the deep red algae flora remained stable. As we revealed that
biomass allocation to blades, stipes and holdfasts as well as the
ability to store blade carbon and nitrogen was kelp species-specific, a
pronounced shift in the functionality of the kelp forest had occurred
over time. We propose that the observed changes in the macroalgal
community are mainly driven by alterations in underwater light climate
as \emph{in situ} data confirmed increasing turbidity and decreasing
irradiance since 2012 and 2017, respectively. As a consequence, the
overall retreat of the kelp forest to lower depth levels seems to be a
result of strong glacial melt and will possibly continue in future with
unforeseen consequences for Arctic coasts and their socio-ecological
fjord systems.

\textbf{Keywords}

macroalgae, depth zonation, biomass, age structure, time series,
Svalbard

\selectlanguage{english}
\FloatBarrier
\end{document}

