How to plot the schematic diagram of the following diagram using tikz latex?

Question

want to plot the schematic diagram of the following diagram using tikz latex, but it is not correct.

\begin{tikzpicture}[node distance=4cm,auto,>=latex',every node/.append style={align=center},int/.style={draw, minimum size=1cm}]
\node [int] (P)             {Phytoplankton (P)};
\node [int, below=of P] (Z) {Zooplankton(Z)};
\node [int, right=of P] (M) {Macrophytes(M)};
\node [int, below=of M] (F) {Fish(F)};
\node [int, right=of F] (W) {Water hyacinth(W)};
\coordinate[right=of M] (out);
 \coordinate[right=of Z] (out);
  \coordinate[right=of F] (out);
  \coordinate[right=of W] (out);
\path[<->, auto=false] (P) edge node {Nutrient/sun light\\competition} (M)
   (M) edge node {competition\\Refuge     \\[2em] } (out) edge  [out=180, in=90] node[below] {competition and\\ Refuge} (W);

\end{tikzpicture}

Answer 1

You are already on a good track.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[node distance=5cm and 4cm,auto,>=latex,
every node/.append style={align=center},int/.style={draw, minimum size=1cm},
broken/.style={thick,blue,dashed}]
  \node [int] (P)             {Phytoplankton (P)};
  \node [int, below=of P] (Z) {Zooplankton (Z)};
  \node [int, right=of P] (M) {Macrophytes (M)};
  \node [int, below=of M] (F) {Fish (F)};
  \path (M) -- (F) node [pos=0.7,int,auto=false] (W) {Water hyacinth (W)};
  \draw[->] (Z) -- (F) node[midway] {Predation} %<- uses auto
  node[midway,above=1cm,dashed,draw] (R1) {Refuge effect}
  node[midway,below=1cm,dashed,draw] (R2) {Refuge effect};
  \draw[->] (P) -- (Z) node[midway,below=2mm,dashed,draw,sloped] (R3) {Refuge effect};
  \draw[->] (P) -- (F);
  \foreach \X/\Y in {P/90,M/90}
  {\draw[->] (\X.\Y) -- ++ (\Y:2) node[midway,swap,align=left]{Death\\ respiration};}
  \foreach \X/\Y in {Z/180,W/0,F/0}
  {\draw[->] (\X.\Y) -- ++ (\Y:2) node[midway,above,align=center]{Death\\ respiration};}
  \foreach \X/\Y in {P/M,P.south east/W.north west,M.south east/W.north}
  {\draw[<->,broken] (\X) -- (\Y) 
   node[midway,above,align=center,sloped] {Nutrient/sun\\ light competition};}
  \draw[broken,->]  (W) -- (R3);
  \draw[broken,->]  (W) -- (R1);
  \draw[broken,->]  (M) -- ++ (4.5,0) |- (R2);
\end{tikzpicture}
\end{document}